use espMqttClient, qos2 fixed

lib/espMqttClient/LICENSE

@@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) 2022 Bert Melis
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

lib/espMqttClient/README.md

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+# espMqttClient
+
+MQTT client library for the Espressif devices ESP8266 and ESP32 on the Arduino framework.
+Aims to be a non-blocking, fully compliant MQTT 3.1.1 client.
+
+![platformio](https://github.com/bertmelis/espMqttClient/actions/workflows/build_platformio.yml/badge.svg)
+![cpplint](https://github.com/bertmelis/espMqttClient/actions/workflows/cpplint.yml/badge.svg)
+![cppcheck](https://github.com/bertmelis/espMqttClient/actions/workflows/cppcheck.yml/badge.svg)
+[![PlatformIO Registry](https://badges.registry.platformio.org/packages/bertmelis/library/espMqttClient.svg)](https://registry.platformio.org/libraries/bertmelis/espMqttClient)
+
+# Features
+
+- MQTT 3.1.1 compliant library
+- Sending and receiving at all QoS levels
+- TCP and TCP/TLS using standard WiFiClient and WiFiClientSecure connections
+- Virtually unlimited incoming and outgoing payload sizes
+- Readable and understandable code
+- Fully async clients available via [AsyncTCP](https://github.com/me-no-dev/AsyncTCP) or [ESPAsnycTCP](https://github.com/me-no-dev/ESPAsyncTCP) (no TLS supported)
+- Supported platforms:
+  - Espressif ESP8266 and ESP32 using the Arduino framework
+- Basic Linux compatibility*. This includes WSL on Windows
+
+    > Linux compatibility is mainly for automatic testing. It relies on a quick and dirty Arduino-style `Client` with a POSIX TCP client underneath and Arduino-style `IPAddress` class. These are lacking many features needed for proper Linux support.
+
+# Documentation
+
+See [documentation](https://www.emelis.net/espMqttClient/) and the [examples](examples/).
+
+## Limitations
+
+### MQTT 3.1.1 Compliancy
+
+Outgoing messages and session data are not stored in non-volatile memory. Any events like loss of power or sudden resets result in loss of data. Despite this limitation, one could still consider this library as fully complaint based on the non normative remark in point 4.1.1 of the specification.
+
+### Non-blocking
+
+This library aims to be fully non-blocking. It is however limited by the underlying `WiFiClient` library which is part of the Arduino framework and has a blocking `connect` method. This is not an issue on ESP32 because the call is offloaded to a separate task. On ESP8266 however, connecting will block until succesful or until the connection timeouts.
+
+If you need a fully asynchronous MQTT client, you can use `espMqttClientAsync` which uses AsyncTCP/ESPAsyncTCP under the hood. These underlying libraries do not support TLS (anymore). I will not provide support TLS for the async client.
+
+# Bugs and feature requests
+
+Please use Github's facilities to get in touch.
+
+# About this library
+
+This client wouldn't exist without [Async-mqtt-client](https://github.com/marvinroger/async-mqtt-client). It has been my go-to MQTT client for many years. It was fast, reliable and had features that were non-existing in alternative libraries. However, the underlying async TCP libraries are lacking updates, especially updates related to secure connections. Adapting this library to use up-to-date TCP clients would not be trivial. I eventually decided to write my own MQTT library, from scratch. 
+
+The result is an almost non-blocking library with no external dependencies. The library is almost a drop-in replacement for the async-mqtt-client except a few parameter type changes (eg. `uint8_t*` instead of `char*` for payloads).
+
+# License
+
+This library is released under the MIT Licence. A copy is included in the repo.
+Parts of this library, most notably the API, are based on [Async MQTT client for ESP8266 and ESP32](https://github.com/marvinroger/async-mqtt-client).

lib/espMqttClient/src/Config.h

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+/*
+Copyright (c) 2022 Bert Melis. All rights reserved.
+
+This work is licensed under the terms of the MIT license.  
+For a copy, see <https://opensource.org/licenses/MIT> or
+the LICENSE file.
+*/
+
+#pragma once
+
+#ifndef EMC_TX_TIMEOUT
+#define EMC_TX_TIMEOUT 5000
+#endif
+
+#ifndef EMC_RX_BUFFER_SIZE
+#define EMC_RX_BUFFER_SIZE 1440
+#endif
+
+#ifndef EMC_TX_BUFFER_SIZE
+#define EMC_TX_BUFFER_SIZE 1440
+#endif
+
+#ifndef EMC_MAX_TOPIC_LENGTH
+#define EMC_MAX_TOPIC_LENGTH 128
+#endif
+
+#ifndef EMC_PAYLOAD_BUFFER_SIZE
+#define EMC_PAYLOAD_BUFFER_SIZE 32
+#endif
+
+#ifndef EMC_MIN_FREE_MEMORY
+#define EMC_MIN_FREE_MEMORY 4096
+#endif
+
+#ifndef EMC_ESP8266_MULTITHREADING
+#define EMC_ESP8266_MULTITHREADING 0
+#endif
+
+#ifndef EMC_ALLOW_NOT_CONNECTED_PUBLISH
+#define EMC_ALLOW_NOT_CONNECTED_PUBLISH 1
+#endif
+
+#ifndef EMC_WAIT_FOR_CONNACK
+#define EMC_WAIT_FOR_CONNACK 1
+#endif
+
+#ifndef EMC_CLIENTID_LENGTH
+// esp8266abc123 and esp32abcdef123456
+#define EMC_CLIENTID_LENGTH 23 + 1
+#endif
+
+#ifndef EMC_TASK_STACK_SIZE
+#define EMC_TASK_STACK_SIZE 5120
+#endif
+
+#ifndef EMC_USE_WATCHDOG
+#define EMC_USE_WATCHDOG 0
+#endif

lib/espMqttClient/src/Helpers.h

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+/*
+Copyright (c) 2022 Bert Melis. All rights reserved.
+
+This work is licensed under the terms of the MIT license.  
+For a copy, see <https://opensource.org/licenses/MIT> or
+the LICENSE file.
+*/
+
+#pragma once
+
+#if defined(ARDUINO_ARCH_ESP32)
+  #include <Arduino.h>  // millis(), ESP.getFreeHeap();
+  #include "freertos/FreeRTOS.h"
+  #include "freertos/task.h"
+  #include "esp_task_wdt.h"
+  #define EMC_SEMAPHORE_TAKE() xSemaphoreTake(_xSemaphore, portMAX_DELAY)
+  #define EMC_SEMAPHORE_GIVE() xSemaphoreGive(_xSemaphore)
+  #define EMC_GET_FREE_MEMORY() std::max(ESP.getMaxAllocHeap(), ESP.getMaxAllocPsram())
+  #define EMC_YIELD() taskYIELD()
+  #define EMC_GENERATE_CLIENTID(x) snprintf(x, EMC_CLIENTID_LENGTH, "esp32%06llx", ESP.getEfuseMac());
+#elif defined(ARDUINO_ARCH_ESP8266)
+  #include <Arduino.h>  // millis(), ESP.getFreeHeap();
+  #if EMC_ESP8266_MULTITHREADING
+    // This lib doesn't run use multithreading on ESP8266
+    // _xSemaphore defined as std::atomic<bool>
+    #define EMC_SEMAPHORE_TAKE() while (_xSemaphore) { /*ESP.wdtFeed();*/ } _xSemaphore = true
+    #define EMC_SEMAPHORE_GIVE() _xSemaphore = false
+  #else
+    #define EMC_SEMAPHORE_TAKE()
+    #define EMC_SEMAPHORE_GIVE()
+  #endif
+  #define EMC_GET_FREE_MEMORY() ESP.getMaxFreeBlockSize()
+  // no need to yield for ESP8266, the Arduino framework does this internally
+  // yielding in async is forbidden (will crash)
+  #define EMC_YIELD()
+  #define EMC_GENERATE_CLIENTID(x) snprintf(x, EMC_CLIENTID_LENGTH, "esp8266%06x", ESP.getChipId());
+#elif defined(__linux__)
+  #include <chrono>  // NOLINT [build/c++11]
+  #include <thread>  // NOLINT [build/c++11] for yield()
+  #define millis() std::chrono::duration_cast<std::chrono::milliseconds>(std::chrono::steady_clock::now().time_since_epoch()).count()
+  #define EMC_GET_FREE_MEMORY() 1000000000
+  #define EMC_YIELD() std::this_thread::yield()
+  #define EMC_GENERATE_CLIENTID(x) snprintf(x, EMC_CLIENTID_LENGTH, "Client%04d%04d%04d", rand()%10000, rand()%10000, rand()%10000)
+  #include <mutex>  // NOLINT [build/c++11]
+    #define EMC_SEMAPHORE_TAKE() mtx.lock();
+    #define EMC_SEMAPHORE_GIVE() mtx.unlock();
+#else
+  #error Target platform not supported
+#endif

lib/espMqttClient/src/Logging.h

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+/*
+Copyright (c) 2022 Bert Melis. All rights reserved.
+
+This work is licensed under the terms of the MIT license.  
+For a copy, see <https://opensource.org/licenses/MIT> or
+the LICENSE file.
+*/
+
+#pragma once
+
+#if defined(ARDUINO_ARCH_ESP32)
+  #include <esp32-hal-log.h>
+  #include "freertos/FreeRTOS.h"
+  #include "freertos/task.h"
+  #if defined(DEBUG_ESP_MQTT_CLIENT)
+  // Logging is en/disabled by Arduino framework macros
+    #define emc_log_i(...) log_i(__VA_ARGS__)
+    #define emc_log_e(...) log_e(__VA_ARGS__)
+    #define emc_log_w(...) log_w(__VA_ARGS__)
+  #else
+  // Logging is disabled
+    #define emc_log_i(...)
+    #define emc_log_e(...)
+    #define emc_log_w(...)
+  #endif
+#elif defined(ARDUINO_ARCH_ESP8266)
+  #if defined(DEBUG_ESP_PORT) && defined(DEBUG_ESP_MQTT_CLIENT)
+    #include <Arduino.h>
+    #define emc_log_i(...) DEBUG_ESP_PORT.printf(__VA_ARGS__); DEBUG_ESP_PORT.print("\n")
+    #define emc_log_e(...) DEBUG_ESP_PORT.printf(__VA_ARGS__); DEBUG_ESP_PORT.print("\n")
+    #define emc_log_w(...) DEBUG_ESP_PORT.printf(__VA_ARGS__); DEBUG_ESP_PORT.print("\n")
+  #else
+    #define emc_log_i(...)
+    #define emc_log_e(...)
+    #define emc_log_w(...)
+  #endif
+#else
+  // when building for PC, always show debug statements as part of testing suite
+  #include <iostream>
+  #define emc_log_i(...) std::cout << "[I] " << __FILE__ ":" << __LINE__ << ": "; printf(__VA_ARGS__); std::cout << std::endl
+  #define emc_log_e(...) std::cout << "[E] " << __FILE__ ":" << __LINE__ << ": "; printf(__VA_ARGS__); std::cout << std::endl
+  #define emc_log_w(...) std::cout << "[W] " << __FILE__ ":" << __LINE__ << ": "; printf(__VA_ARGS__); std::cout << std::endl
+#endif

lib/espMqttClient/src/MqttClient.cpp

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+/*
+Copyright (c) 2022 Bert Melis. All rights reserved.
+
+This work is licensed under the terms of the MIT license.  
+For a copy, see <https://opensource.org/licenses/MIT> or
+the LICENSE file.
+*/
+
+#include "MqttClient.h"
+
+using espMqttClientInternals::Packet;
+using espMqttClientInternals::PacketType;
+using espMqttClientTypes::DisconnectReason;
+using espMqttClientTypes::Error;
+
+MqttClient::MqttClient(espMqttClientTypes::UseInternalTask useInternalTask, uint8_t priority, uint8_t core)
+#if defined(ARDUINO_ARCH_ESP32)
+    : _useInternalTask(useInternalTask)
+    , _transport(nullptr)
+#else
+    : _transport(nullptr)
+#endif
+    , _onConnectCallback(nullptr)
+    , _onDisconnectCallback(nullptr)
+    , _onSubscribeCallback(nullptr)
+    , _onUnsubscribeCallback(nullptr)
+    , _onMessageCallback(nullptr)
+    , _onPublishCallback(nullptr)
+    , _onErrorCallback(nullptr)
+    , _clientId(nullptr)
+    , _ip()
+    , _host(nullptr)
+    , _port(1883)
+    , _useIp(false)
+    , _keepAlive(15000)
+    , _cleanSession(true)
+    , _username(nullptr)
+    , _password(nullptr)
+    , _willTopic(nullptr)
+    , _willPayload(nullptr)
+    , _willPayloadLength(0)
+    , _willQos(0)
+    , _willRetain(false)
+    , _timeout(EMC_TX_TIMEOUT)
+    , _state(State::disconnected)
+    , _generatedClientId{0}
+    , _packetId(0)
+#if defined(ARDUINO_ARCH_ESP32)
+    , _xSemaphore(nullptr)
+    , _taskHandle(nullptr)
+#endif
+    , _rxBuffer{0}
+    , _outbox()
+    , _bytesSent(0)
+    , _parser()
+    , _lastClientActivity(0)
+    , _lastServerActivity(0)
+    , _pingSent(false)
+    , _disconnectReason(DisconnectReason::TCP_DISCONNECTED)
+#if defined(ARDUINO_ARCH_ESP32) && ARDUHAL_LOG_LEVEL >= ARDUHAL_LOG_LEVEL_INFO
+    , _highWaterMark(4294967295)
+#endif
+{
+    EMC_GENERATE_CLIENTID(_generatedClientId);
+#if defined(ARDUINO_ARCH_ESP32)
+    _xSemaphore = xSemaphoreCreateMutex();
+    EMC_SEMAPHORE_GIVE(); // release before first use
+    if (_useInternalTask == espMqttClientTypes::UseInternalTask::YES) {
+        xTaskCreatePinnedToCore((TaskFunction_t)_loop, "mqttclient", EMC_TASK_STACK_SIZE, this, priority, &_taskHandle, core);
+    }
+#else
+    (void)useInternalTask;
+    (void)priority;
+    (void)core;
+#endif
+    _clientId = _generatedClientId;
+}
+
+MqttClient::~MqttClient() {
+    disconnect(true);
+    _clearQueue(2);
+#if defined(ARDUINO_ARCH_ESP32)
+    vSemaphoreDelete(_xSemaphore);
+    if (_useInternalTask == espMqttClientTypes::UseInternalTask::YES) {
+#if EMC_USE_WATCHDOG
+        esp_task_wdt_delete(_taskHandle); // not sure if this is really needed
+#endif
+        vTaskDelete(_taskHandle);
+    }
+#endif
+}
+
+bool MqttClient::connected() const {
+    if (_state == State::connected)
+        return true;
+    return false;
+}
+
+bool MqttClient::disconnected() const {
+    if (_state == State::disconnected)
+        return true;
+    return false;
+}
+
+bool MqttClient::connect() {
+    bool result = true;
+    if (_state == State::disconnected) {
+        EMC_SEMAPHORE_TAKE();
+        if (_addPacketFront(_cleanSession,
+                            _username,
+                            _password,
+                            _willTopic,
+                            _willRetain,
+                            _willQos,
+                            _willPayload,
+                            _willPayloadLength,
+                            (uint16_t)(_keepAlive / 1000), // 32b to 16b doesn't overflow because it comes from 16b orignally
+                            _clientId)) {
+#if defined(ARDUINO_ARCH_ESP32)
+            if (_useInternalTask == espMqttClientTypes::UseInternalTask::YES) {
+                vTaskResume(_taskHandle);
+            }
+#endif
+            _state = State::connectingTcp1;
+        } else {
+            EMC_SEMAPHORE_GIVE();
+            emc_log_e("Could not create CONNECT packet");
+            _onError(0, Error::OUT_OF_MEMORY);
+            result = false;
+        }
+        EMC_SEMAPHORE_GIVE();
+    }
+    return result;
+}
+
+bool MqttClient::disconnect(bool force) {
+    if (force && _state != State::disconnected && _state != State::disconnectingTcp1 && _state != State::disconnectingTcp2) {
+        _state = State::disconnectingTcp1;
+        return true;
+    }
+    if (!force && _state == State::connected) {
+        _state = State::disconnectingMqtt1;
+        return true;
+    }
+    return false;
+}
+
+uint16_t MqttClient::publish(const char * topic, uint8_t qos, bool retain, const uint8_t * payload, size_t length) {
+#if !EMC_ALLOW_NOT_CONNECTED_PUBLISH
+    if (_state != State::connected) {
+#else
+    if (_state > State::connected) {
+#endif
+        return 0;
+    }
+    uint16_t packetId = (qos > 0) ? _getNextPacketId() : 1;
+    EMC_SEMAPHORE_TAKE();
+    if (!_addPacket(packetId, topic, payload, length, qos, retain)) {
+        emc_log_e("Could not create PUBLISH packet");
+        _onError(packetId, Error::OUT_OF_MEMORY);
+        packetId = 0;
+    }
+    EMC_SEMAPHORE_GIVE();
+    return packetId;
+}
+
+uint16_t MqttClient::publish(const char * topic, uint8_t qos, bool retain, const char * payload) {
+    size_t len = strlen(payload);
+    return publish(topic, qos, retain, reinterpret_cast<const uint8_t *>(payload), len);
+}
+
+uint16_t MqttClient::publish(const char * topic, uint8_t qos, bool retain, espMqttClientTypes::PayloadCallback callback, size_t length) {
+#if !EMC_ALLOW_NOT_CONNECTED_PUBLISH
+    if (_state != State::connected) {
+#else
+    if (_state > State::connected) {
+#endif
+        return 0;
+    }
+    uint16_t packetId = (qos > 0) ? _getNextPacketId() : 1;
+    EMC_SEMAPHORE_TAKE();
+    if (!_addPacket(packetId, topic, callback, length, qos, retain)) {
+        emc_log_e("Could not create PUBLISH packet");
+        _onError(packetId, Error::OUT_OF_MEMORY);
+        packetId = 0;
+    }
+    EMC_SEMAPHORE_GIVE();
+    return packetId;
+}
+
+void MqttClient::clearQueue(bool deleteSessionData) {
+    _clearQueue(deleteSessionData ? 2 : 0);
+}
+
+const char * MqttClient::getClientId() const {
+    return _clientId;
+}
+
+void MqttClient::loop() {
+    switch (_state) {
+    case State::disconnected:
+#if defined(ARDUINO_ARCH_ESP32)
+        if (_useInternalTask == espMqttClientTypes::UseInternalTask::YES) {
+            vTaskSuspend(_taskHandle);
+        }
+#endif
+        break;
+    case State::connectingTcp1:
+        if (_useIp ? _transport->connect(_ip, _port) : _transport->connect(_host, _port)) {
+            _state = State::connectingTcp2;
+        } else {
+            _state            = State::disconnectingTcp1;
+            _disconnectReason = DisconnectReason::TCP_DISCONNECTED;
+            break;
+        }
+        // Falling through to speed up connecting on blocking transport 'connect' implementations
+        [[fallthrough]];
+    case State::connectingTcp2:
+        if (_transport->connected()) {
+            _parser.reset();
+            _lastClientActivity = _lastServerActivity = millis();
+            _state                                    = State::connectingMqtt;
+        }
+        break;
+    case State::connectingMqtt:
+#if EMC_WAIT_FOR_CONNACK
+        if (_transport->connected()) {
+            _sendPacket();
+            _checkIncoming();
+            _checkPing();
+        } else {
+            _state            = State::disconnectingTcp1;
+            _disconnectReason = DisconnectReason::TCP_DISCONNECTED;
+        }
+        break;
+#else
+        // receipt of CONNACK packet will set state to CONNECTED
+        // client however is allowed to send packets before CONNACK is received
+        // so we fall through to 'connected'
+        [[fallthrough]];
+#endif
+    case State::connected:
+        [[fallthrough]];
+    case State::disconnectingMqtt2:
+        if (_transport->connected()) {
+            // CONNECT packet is first in the queue
+            _checkOutbox();
+            _checkIncoming();
+            _checkPing();
+            _checkTimeout();
+        } else {
+            _state            = State::disconnectingTcp1;
+            _disconnectReason = DisconnectReason::TCP_DISCONNECTED;
+        }
+        break;
+    case State::disconnectingMqtt1:
+        EMC_SEMAPHORE_TAKE();
+        if (_outbox.empty()) {
+            if (!_addPacket(PacketType.DISCONNECT)) {
+                EMC_SEMAPHORE_GIVE();
+                emc_log_e("Could not create DISCONNECT packet");
+                _onError(0, Error::OUT_OF_MEMORY);
+            } else {
+                _state = State::disconnectingMqtt2;
+            }
+        }
+        EMC_SEMAPHORE_GIVE();
+        _checkOutbox();
+        _checkIncoming();
+        _checkPing();
+        _checkTimeout();
+        break;
+    case State::disconnectingTcp1:
+        _transport->stop();
+        _state = State::disconnectingTcp2;
+        break; // keep break to accomodate async clients
+    case State::disconnectingTcp2:
+        if (_transport->disconnected()) {
+            _clearQueue(0);
+            _bytesSent = 0;
+            _state     = State::disconnected;
+            if (_onDisconnectCallback)
+                _onDisconnectCallback(_disconnectReason);
+        }
+        break;
+        // all cases covered, no default case
+    }
+    EMC_YIELD();
+#if defined(ARDUINO_ARCH_ESP32) && ARDUHAL_LOG_LEVEL >= ARDUHAL_LOG_LEVEL_INFO
+    size_t waterMark = uxTaskGetStackHighWaterMark(NULL);
+    if (waterMark < _highWaterMark) {
+        _highWaterMark = waterMark;
+        emc_log_i("Stack usage: %zu/%i", EMC_TASK_STACK_SIZE - _highWaterMark, EMC_TASK_STACK_SIZE);
+    }
+#endif
+}
+
+#if defined(ARDUINO_ARCH_ESP32)
+void MqttClient::_loop(MqttClient * c) {
+#if EMC_USE_WATCHDOG
+    if (esp_task_wdt_add(NULL) != ESP_OK) {
+        emc_log_e("Failed to add async task to WDT");
+    }
+#endif
+    for (;;) {
+        c->loop();
+#if EMC_USE_WATCHDOG
+        esp_task_wdt_reset();
+#endif
+    }
+}
+#endif
+
+uint16_t MqttClient::_getNextPacketId() {
+    uint16_t packetId = 0;
+    EMC_SEMAPHORE_TAKE();
+    // cppcheck-suppress knownConditionTrueFalse
+    packetId = (++_packetId == 0) ? ++_packetId : _packetId;
+    EMC_SEMAPHORE_GIVE();
+    return packetId;
+}
+
+void MqttClient::_checkOutbox() {
+    while (_sendPacket() > 0) {
+        if (!_advanceOutbox()) {
+            break;
+        }
+    }
+}
+
+int MqttClient::_sendPacket() {
+    EMC_SEMAPHORE_TAKE();
+    OutgoingPacket * packet = _outbox.getCurrent();
+
+    int32_t wantToWrite = 0;
+    int32_t written     = 0;
+    if (packet && (wantToWrite == written)) {
+        // mixing signed with unsigned here but safe because of MQTT packet size limits
+        wantToWrite = packet->packet.available(_bytesSent);
+        if (wantToWrite == 0) {
+            EMC_SEMAPHORE_GIVE();
+            return 0;
+        }
+        written = _transport->write(packet->packet.data(_bytesSent), wantToWrite);
+        if (written < 0) {
+            emc_log_w("Write error, check connection");
+            EMC_SEMAPHORE_GIVE();
+            return -1;
+        }
+        packet->timeSent    = millis();
+        _lastClientActivity = millis();
+        _bytesSent += written;
+        emc_log_i("tx %zu/%zu (%02x)", _bytesSent, packet->packet.size(), packet->packet.packetType());
+    }
+    EMC_SEMAPHORE_GIVE();
+    return written;
+}
+
+bool MqttClient::_advanceOutbox() {
+    EMC_SEMAPHORE_TAKE();
+    OutgoingPacket * packet = _outbox.getCurrent();
+    if (packet && _bytesSent == packet->packet.size()) {
+        if ((packet->packet.packetType()) == PacketType.DISCONNECT) {
+            _state            = State::disconnectingTcp1;
+            _disconnectReason = DisconnectReason::USER_OK;
+        }
+        if (packet->packet.removable()) {
+            _outbox.removeCurrent();
+        } else {
+            // we already set 'dup' here, in case we have to retry
+            if ((packet->packet.packetType()) == PacketType.PUBLISH)
+                packet->packet.setDup();
+            _outbox.next();
+        }
+        packet     = _outbox.getCurrent();
+        _bytesSent = 0;
+    }
+    EMC_SEMAPHORE_GIVE();
+    return packet;
+}
+
+void MqttClient::_checkIncoming() {
+    int32_t remainingBufferLength = _transport->read(_rxBuffer, EMC_RX_BUFFER_SIZE);
+    if (remainingBufferLength > 0) {
+        _lastServerActivity = millis();
+        emc_log_i("rx len %i", remainingBufferLength);
+        size_t bytesParsed = 0;
+        size_t index       = 0;
+        while (remainingBufferLength > 0) {
+            espMqttClientInternals::ParserResult result = _parser.parse(&_rxBuffer[index], remainingBufferLength, &bytesParsed);
+            if (result == espMqttClientInternals::ParserResult::packet) {
+                espMqttClientInternals::MQTTPacketType packetType = _parser.getPacket().fixedHeader.packetType & 0xF0;
+                if (_state == State::connectingMqtt && packetType != PacketType.CONNACK) {
+                    emc_log_w("Disconnecting, expected CONNACK - protocol error");
+                    _state = State::disconnectingTcp1;
+                    return;
+                }
+                switch (packetType & 0xF0) {
+                case PacketType.CONNACK:
+                    _onConnack();
+                    if (_state != State::connected) {
+                        return;
+                    }
+                    break;
+                case PacketType.PUBLISH:
+                    if (_state >= State::disconnectingMqtt1)
+                        break; // stop processing incoming once user has called disconnect
+                    _onPublish();
+                    break;
+                case PacketType.PUBACK:
+                    _onPuback();
+                    break;
+                case PacketType.PUBREC:
+                    _onPubrec();
+                    break;
+                case PacketType.PUBREL:
+                    _onPubrel();
+                    break;
+                case PacketType.PUBCOMP:
+                    _onPubcomp();
+                    break;
+                case PacketType.SUBACK:
+                    _onSuback();
+                    break;
+                case PacketType.UNSUBACK:
+                    _onUnsuback();
+                    break;
+                case PacketType.PINGRESP:
+                    _pingSent = false;
+                    break;
+                }
+            } else if (result == espMqttClientInternals::ParserResult::protocolError) {
+                emc_log_w("Disconnecting, protocol error");
+                _state            = State::disconnectingTcp1;
+                _disconnectReason = DisconnectReason::TCP_DISCONNECTED;
+                return;
+            }
+            remainingBufferLength -= bytesParsed;
+            index += bytesParsed;
+            emc_log_i("Parsed %zu - remaining %i", bytesParsed, remainingBufferLength);
+            bytesParsed = 0;
+        }
+    }
+}
+
+void MqttClient::_checkPing() {
+    if (_keepAlive == 0)
+        return; // keepalive is disabled
+
+    uint32_t currentMillis = millis();
+
+    // disconnect when server was inactive for twice the keepalive time
+    if (currentMillis - _lastServerActivity > 2 * _keepAlive) {
+        emc_log_w("Disconnecting, server exceeded keepalive");
+        _state            = State::disconnectingTcp1;
+        _disconnectReason = DisconnectReason::TCP_DISCONNECTED;
+        return;
+    }
+
+    // send ping when client was inactive during the keepalive time
+    // or when server hasn't responded within keepalive time (typically due to QOS 0)
+    if (!_pingSent && ((currentMillis - _lastClientActivity > _keepAlive) || (currentMillis - _lastServerActivity > _keepAlive))) {
+        EMC_SEMAPHORE_TAKE();
+        if (!_addPacket(PacketType.PINGREQ)) {
+            EMC_SEMAPHORE_GIVE();
+            emc_log_e("Could not create PING packet");
+            return;
+        }
+        EMC_SEMAPHORE_GIVE();
+        _pingSent = true;
+    }
+}
+
+void MqttClient::_checkTimeout() {
+    EMC_SEMAPHORE_TAKE();
+    espMqttClientInternals::Outbox<OutgoingPacket>::Iterator it = _outbox.front();
+    // check that we're not busy sending
+    // don't check when first item hasn't been sent yet
+    if (it && _bytesSent == 0 && it.get() != _outbox.getCurrent()) {
+        if (millis() - it.get()->timeSent > _timeout) {
+            emc_log_w("Packet ack timeout, retrying");
+            _outbox.resetCurrent();
+        }
+    }
+    EMC_SEMAPHORE_GIVE();
+}
+
+void MqttClient::_onConnack() {
+    if (_parser.getPacket().variableHeader.fixed.connackVarHeader.returnCode == 0x00) {
+        _pingSent = false; // reset after keepalive timeout disconnect
+        _state    = State::connected;
+        _advanceOutbox();
+        if (_parser.getPacket().variableHeader.fixed.connackVarHeader.sessionPresent == 0) {
+            _clearQueue(1);
+        }
+        if (_onConnectCallback) {
+            _onConnectCallback(_parser.getPacket().variableHeader.fixed.connackVarHeader.sessionPresent);
+        }
+    } else {
+        _state = State::disconnectingTcp1;
+        // cast is safe because the parser already checked for a valid return code
+        _disconnectReason = static_cast<DisconnectReason>(_parser.getPacket().variableHeader.fixed.connackVarHeader.returnCode);
+    }
+}
+
+void MqttClient::_onPublish() {
+    espMqttClientInternals::IncomingPacket p        = _parser.getPacket();
+    uint8_t                                qos      = p.qos();
+    bool                                   retain   = p.retain();
+    bool                                   dup      = p.dup();
+    uint16_t                               packetId = p.variableHeader.fixed.packetId;
+    bool                                   callback = true;
+    if (qos == 1) {
+        if (p.payload.index + p.payload.length == p.payload.total) {
+            EMC_SEMAPHORE_TAKE();
+            if (!_addPacket(PacketType.PUBACK, packetId)) {
+                emc_log_e("Could not create PUBACK packet");
+            }
+            EMC_SEMAPHORE_GIVE();
+        }
+    } else if (qos == 2) {
+        EMC_SEMAPHORE_TAKE();
+        espMqttClientInternals::Outbox<OutgoingPacket>::Iterator it = _outbox.front();
+        while (it) {
+            if ((it.get()->packet.packetType()) == PacketType.PUBREC && it.get()->packet.packetId() == packetId) {
+                callback = false;
+                _outbox.remove(it);
+                emc_log_e("QoS2 packet previously delivered");
+                break;
+            }
+            ++it;
+        }
+        if (p.payload.index + p.payload.length == p.payload.total) {
+            if (!_addPacket(PacketType.PUBREC, packetId)) {
+                emc_log_e("Could not create PUBREC packet");
+            }
+        }
+        EMC_SEMAPHORE_GIVE();
+    }
+    if (callback && _onMessageCallback)
+        _onMessageCallback({qos, dup, retain, packetId}, p.variableHeader.topic, p.payload.data, p.payload.length, p.payload.index, p.payload.total);
+}
+
+void MqttClient::_onPuback() {
+    bool     callback  = false;
+    uint16_t idToMatch = _parser.getPacket().variableHeader.fixed.packetId;
+    EMC_SEMAPHORE_TAKE();
+    espMqttClientInternals::Outbox<OutgoingPacket>::Iterator it = _outbox.front();
+    while (it) {
+        // PUBACKs come in the order PUBs are sent. So we only check the first PUB packet in outbox
+        // if it doesn't match the ID, return
+        if ((it.get()->packet.packetType()) == PacketType.PUBLISH) {
+            if (it.get()->packet.packetId() == idToMatch) {
+                callback = true;
+                _outbox.remove(it);
+                break;
+            }
+            emc_log_w("Received out of order PUBACK");
+            break;
+        }
+        ++it;
+    }
+    EMC_SEMAPHORE_GIVE();
+    if (callback) {
+        if (_onPublishCallback)
+            _onPublishCallback(idToMatch);
+    } else {
+        emc_log_w("No matching PUBLISH packet found");
+    }
+}
+
+void MqttClient::_onPubrec() {
+    bool     success   = false;
+    uint16_t idToMatch = _parser.getPacket().variableHeader.fixed.packetId;
+    EMC_SEMAPHORE_TAKE();
+    espMqttClientInternals::Outbox<OutgoingPacket>::Iterator it = _outbox.front();
+    while (it) {
+        // PUBRECs come in the order PUBs are sent. So we only check the first PUB packet in outbox
+        // if it doesn't match the ID, return
+        if ((it.get()->packet.packetType()) == PacketType.PUBLISH) {
+            if (it.get()->packet.packetId() == idToMatch) {
+                if (!_addPacket(PacketType.PUBREL, idToMatch)) {
+                    emc_log_e("Could not create PUBREL packet");
+                }
+                _outbox.remove(it);
+                success = true;
+                break;
+            }
+            emc_log_w("Received out of order PUBREC");
+            break;
+        }
+        ++it;
+    }
+    if (!success) {
+        emc_log_w("No matching PUBLISH packet found");
+    }
+    EMC_SEMAPHORE_GIVE();
+}
+
+void MqttClient::_onPubrel() {
+    bool     success   = false;
+    uint16_t idToMatch = _parser.getPacket().variableHeader.fixed.packetId;
+    EMC_SEMAPHORE_TAKE();
+    espMqttClientInternals::Outbox<OutgoingPacket>::Iterator it = _outbox.front();
+    while (it) {
+        // PUBRELs come in the order PUBRECs are sent. So we only check the first PUBREC packet in outbox
+        // if it doesn't match the ID, return
+        if ((it.get()->packet.packetType()) == PacketType.PUBREC) {
+            if (it.get()->packet.packetId() == idToMatch) {
+                if (!_addPacket(PacketType.PUBCOMP, idToMatch)) {
+                    emc_log_e("Could not create PUBCOMP packet");
+                }
+                _outbox.remove(it);
+                success = true;
+                break;
+            }
+            emc_log_w("Received out of order PUBREL");
+            break;
+        }
+        ++it;
+    }
+    if (!success) {
+        emc_log_w("No matching PUBREC packet found");
+    }
+    EMC_SEMAPHORE_GIVE();
+}
+
+void MqttClient::_onPubcomp() {
+    bool callback = false;
+    EMC_SEMAPHORE_TAKE();
+    espMqttClientInternals::Outbox<OutgoingPacket>::Iterator it        = _outbox.front();
+    uint16_t                                                 idToMatch = _parser.getPacket().variableHeader.fixed.packetId;
+    while (it) {
+        // PUBCOMPs come in the order PUBRELs are sent. So we only check the first PUBREL packet in outbox
+        // if it doesn't match the ID, return
+        if ((it.get()->packet.packetType()) == PacketType.PUBREL) {
+            if (it.get()->packet.packetId() == idToMatch) {
+                // if (!_addPacket(PacketType.PUBCOMP, idToMatch)) {
+                //     emc_log_e("Could not create PUBCOMP packet");
+                // }
+                callback = true;
+                _outbox.remove(it);
+                break;
+            }
+            emc_log_w("Received out of order PUBCOMP");
+            break;
+        }
+        ++it;
+    }
+    EMC_SEMAPHORE_GIVE();
+    if (callback) {
+        if (_onPublishCallback)
+            _onPublishCallback(idToMatch);
+    } else {
+        emc_log_w("No matching PUBREL packet found");
+    }
+}
+
+void MqttClient::_onSuback() {
+    bool     callback  = false;
+    uint16_t idToMatch = _parser.getPacket().variableHeader.fixed.packetId;
+    EMC_SEMAPHORE_TAKE();
+    espMqttClientInternals::Outbox<OutgoingPacket>::Iterator it = _outbox.front();
+    while (it) {
+        if (((it.get()->packet.packetType()) == PacketType.SUBSCRIBE) && it.get()->packet.packetId() == idToMatch) {
+            callback = true;
+            _outbox.remove(it);
+            break;
+        }
+        ++it;
+    }
+    EMC_SEMAPHORE_GIVE();
+    if (callback) {
+        if (_onSubscribeCallback)
+            _onSubscribeCallback(idToMatch,
+                                 reinterpret_cast<const espMqttClientTypes::SubscribeReturncode *>(_parser.getPacket().payload.data),
+                                 _parser.getPacket().payload.total);
+    } else {
+        emc_log_w("received SUBACK without SUB");
+    }
+}
+
+void MqttClient::_onUnsuback() {
+    bool callback = false;
+    EMC_SEMAPHORE_TAKE();
+    espMqttClientInternals::Outbox<OutgoingPacket>::Iterator it        = _outbox.front();
+    uint16_t                                                 idToMatch = _parser.getPacket().variableHeader.fixed.packetId;
+    while (it) {
+        if (it.get()->packet.packetId() == idToMatch) {
+            callback = true;
+            _outbox.remove(it);
+            break;
+        }
+        ++it;
+    }
+    EMC_SEMAPHORE_GIVE();
+    if (callback) {
+        if (_onUnsubscribeCallback)
+            _onUnsubscribeCallback(idToMatch);
+    } else {
+        emc_log_w("received UNSUBACK without UNSUB");
+    }
+}
+
+uint16_t MqttClient::getQueue() const {
+    EMC_SEMAPHORE_TAKE();
+    espMqttClientInternals::Outbox<OutgoingPacket>::Iterator it    = _outbox.front();
+    uint16_t                                                 count = 0;
+    while (it) {
+        ++count;
+        ++it;
+    }
+    EMC_SEMAPHORE_GIVE();
+    return count;
+}
+
+void MqttClient::_clearQueue(int clearData) {
+    emc_log_i("clearing queue (clear session: %d)", clearData);
+    EMC_SEMAPHORE_TAKE();
+    espMqttClientInternals::Outbox<OutgoingPacket>::Iterator it = _outbox.front();
+    if (clearData == 0) {
+        // keep PUB (qos > 0, aka packetID != 0), PUBREC and PUBREL
+        // Spec only mentions PUB and PUBREL but this lib implements method B from point 4.3.3 (Fig. 4.3)
+        // and stores the packet id in the PUBREC packet. So we also must keep PUBREC.
+        while (it) {
+            espMqttClientInternals::MQTTPacketType type = it.get()->packet.packetType();
+            if (type == PacketType.PUBREC || type == PacketType.PUBREL || (type == PacketType.PUBLISH && it.get()->packet.packetId() != 0)) {
+                ++it;
+            } else {
+                _outbox.remove(it);
+            }
+        }
+    } else if (clearData == 1) {
+        // keep PUB
+        while (it) {
+            if (it.get()->packet.packetType() == PacketType.PUBLISH) {
+                ++it;
+            } else {
+                _outbox.remove(it);
+            }
+        }
+    } else { // clearData == 2
+        while (it) {
+            _outbox.remove(it);
+        }
+    }
+    EMC_SEMAPHORE_GIVE();
+}
+
+void MqttClient::_onError(uint16_t packetId, espMqttClientTypes::Error error) {
+    if (_onErrorCallback) {
+        _onErrorCallback(packetId, error);
+    }
+}

lib/espMqttClient/src/MqttClient.h

@@ -0,0 +1,190 @@
+/*
+Copyright (c) 2022 Bert Melis. All rights reserved.
+
+API is based on the original work of Marvin Roger:
+https://github.com/marvinroger/async-mqtt-client
+
+This work is licensed under the terms of the MIT license.  
+For a copy, see <https://opensource.org/licenses/MIT> or
+the LICENSE file.
+*/
+
+#pragma once
+
+#include <atomic>
+#include <utility>
+
+#include "Helpers.h"
+#include "Config.h"
+#include "TypeDefs.h"
+#include "Logging.h"
+#include "Outbox.h"
+#include "Packets/Packet.h"
+#include "Packets/Parser.h"
+#include "Transport/Transport.h"
+
+class MqttClient {
+ public:
+  virtual ~MqttClient();
+  bool connected() const;
+  bool disconnected() const;
+  bool connect();
+  bool disconnect(bool force = false);
+  template <typename... Args>
+  uint16_t subscribe(const char* topic, uint8_t qos, Args&&... args) {
+    uint16_t packetId = _getNextPacketId();
+    if (_state != State::connected) {
+      packetId = 0;
+    } else {
+      EMC_SEMAPHORE_TAKE();
+      if (!_addPacket(packetId, topic, qos, std::forward<Args>(args) ...)) {
+        emc_log_e("Could not create SUBSCRIBE packet");
+        packetId = 0;
+      }
+      EMC_SEMAPHORE_GIVE();
+    }
+    return packetId;
+  }
+  template <typename... Args>
+  uint16_t unsubscribe(const char* topic, Args&&... args) {
+    uint16_t packetId = _getNextPacketId();
+    if (_state != State::connected) {
+      packetId = 0;
+    } else {
+      EMC_SEMAPHORE_TAKE();
+      if (!_addPacket(packetId, topic, std::forward<Args>(args) ...)) {
+        emc_log_e("Could not create UNSUBSCRIBE packet");
+        packetId = 0;
+      }
+      EMC_SEMAPHORE_GIVE();
+    }
+    return packetId;
+  }
+  uint16_t publish(const char* topic, uint8_t qos, bool retain, const uint8_t* payload, size_t length);
+  uint16_t publish(const char* topic, uint8_t qos, bool retain, const char* payload);
+  uint16_t publish(const char* topic, uint8_t qos, bool retain, espMqttClientTypes::PayloadCallback callback, size_t length);
+  void clearQueue(bool deleteSessionData = false);  // Not MQTT compliant and may cause unpredictable results when `deleteSessionData` = true!
+  const char* getClientId() const;
+  uint16_t getQueue() const;
+  void loop();
+
+ protected:
+  explicit MqttClient(espMqttClientTypes::UseInternalTask useInternalTask, uint8_t priority = 1, uint8_t core = 1);
+  espMqttClientTypes::UseInternalTask _useInternalTask;
+  espMqttClientInternals::Transport* _transport;
+
+  espMqttClientTypes::OnConnectCallback _onConnectCallback;
+  espMqttClientTypes::OnDisconnectCallback _onDisconnectCallback;
+  espMqttClientTypes::OnSubscribeCallback _onSubscribeCallback;
+  espMqttClientTypes::OnUnsubscribeCallback _onUnsubscribeCallback;
+  espMqttClientTypes::OnMessageCallback _onMessageCallback;
+  espMqttClientTypes::OnPublishCallback _onPublishCallback;
+  espMqttClientTypes::OnErrorCallback _onErrorCallback;
+  typedef void(*mqttClientHook)(void*);
+  const char* _clientId;
+  IPAddress _ip;
+  const char* _host;
+  uint16_t _port;
+  bool _useIp;
+  uint32_t _keepAlive;
+  bool _cleanSession;
+  const char* _username;
+  const char* _password;
+  const char* _willTopic;
+  const uint8_t* _willPayload;
+  uint16_t _willPayloadLength;
+  uint8_t _willQos;
+  bool _willRetain;
+  uint32_t _timeout;
+
+  // state is protected to allow state changes by the transport system, defined in child classes
+  // eg. to allow AsyncTCP
+  enum class State {
+    disconnected =       0,
+    connectingTcp1 =     1,
+    connectingTcp2 =     2,
+    connectingMqtt =     3,
+    connected =          4,
+    disconnectingMqtt1 = 5,
+    disconnectingMqtt2 = 6,
+    disconnectingTcp1 =  7,
+    disconnectingTcp2 =  8
+  };
+  std::atomic<State> _state;
+
+ private:
+  char _generatedClientId[EMC_CLIENTID_LENGTH];
+  uint16_t _packetId;
+
+#if defined(ARDUINO_ARCH_ESP32)
+  SemaphoreHandle_t _xSemaphore;
+  TaskHandle_t _taskHandle;
+  static void _loop(MqttClient* c);
+#elif defined(ARDUINO_ARCH_ESP8266) && EMC_ESP8266_MULTITHREADING
+  std::atomic<bool> _xSemaphore = false;
+#elif defined(__linux__)
+  std::mutex mtx;
+#endif
+
+  uint8_t _rxBuffer[EMC_RX_BUFFER_SIZE];
+  struct OutgoingPacket {
+    uint32_t timeSent;
+    espMqttClientInternals::Packet packet;
+    template <typename... Args>
+    OutgoingPacket(uint32_t t, espMqttClientTypes::Error error, Args&&... args) :
+      timeSent(t),
+      packet(error, std::forward<Args>(args) ...) {}
+  };
+  espMqttClientInternals::Outbox<OutgoingPacket> _outbox;
+  size_t _bytesSent;
+  espMqttClientInternals::Parser _parser;
+  uint32_t _lastClientActivity;
+  uint32_t _lastServerActivity;
+  bool _pingSent;
+  espMqttClientTypes::DisconnectReason _disconnectReason;
+
+  uint16_t _getNextPacketId();
+
+  template <typename... Args>
+  bool _addPacket(Args&&... args) {
+    espMqttClientTypes::Error error(espMqttClientTypes::Error::SUCCESS);
+    espMqttClientInternals::Outbox<OutgoingPacket>::Iterator it = _outbox.emplace(0, error, std::forward<Args>(args) ...);
+    if (it && error == espMqttClientTypes::Error::SUCCESS) return true;
+    return false;
+  }
+
+  template <typename... Args>
+  bool _addPacketFront(Args&&... args) {
+    espMqttClientTypes::Error error(espMqttClientTypes::Error::SUCCESS);
+    espMqttClientInternals::Outbox<OutgoingPacket>::Iterator it = _outbox.emplaceFront(0, error, std::forward<Args>(args) ...);
+    if (it && error == espMqttClientTypes::Error::SUCCESS) return true;
+    return false;
+  }
+
+  void _checkOutbox();
+  int _sendPacket();
+  bool _advanceOutbox();
+  void _checkIncoming();
+  void _checkPing();
+  void _checkTimeout();
+
+  void _onConnack();
+  void _onPublish();
+  void _onPuback();
+  void _onPubrec();
+  void _onPubrel();
+  void _onPubcomp();
+  void _onSuback();
+  void _onUnsuback();
+
+  void _clearQueue(int clearData);  // 0: keep session,
+                                    // 1: keep only PUBLISH qos > 0
+                                    // 2: delete all
+  void _onError(uint16_t packetId, espMqttClientTypes::Error error);
+
+  #if defined(ARDUINO_ARCH_ESP32)
+  #if ARDUHAL_LOG_LEVEL >= ARDUHAL_LOG_LEVEL_INFO
+  size_t _highWaterMark;
+  #endif
+  #endif
+};

lib/espMqttClient/src/MqttClientSetup.h

@@ -0,0 +1,116 @@
+/*
+Copyright (c) 2022 Bert Melis. All rights reserved.
+
+API is based on the original work of Marvin Roger:
+https://github.com/marvinroger/async-mqtt-client
+
+This work is licensed under the terms of the MIT license.  
+For a copy, see <https://opensource.org/licenses/MIT> or
+the LICENSE file.
+*/
+
+#pragma once
+
+#include "MqttClient.h"
+
+template <typename T>
+class MqttClientSetup : public MqttClient {
+ public:
+  T& setKeepAlive(uint16_t keepAlive) {
+    _keepAlive = keepAlive * 1000;  // s to ms conversion, will also do 16 to 32 bit conversion
+    return static_cast<T&>(*this);
+  }
+
+  T& setClientId(const char* clientId) {
+    _clientId = clientId;
+    return static_cast<T&>(*this);
+  }
+
+  T& setCleanSession(bool cleanSession) {
+    _cleanSession = cleanSession;
+    return static_cast<T&>(*this);
+  }
+
+  T& setCredentials(const char* username, const char* password) {
+    _username = username;
+    _password = password;
+    return static_cast<T&>(*this);
+  }
+
+  T& setWill(const char* topic, uint8_t qos, bool retain, const uint8_t* payload, size_t length) {
+    _willTopic = topic;
+    _willQos = qos;
+    _willRetain = retain;
+    _willPayload = payload;
+    if (!_willPayload) {
+      _willPayloadLength = 0;
+    } else {
+      _willPayloadLength = length;
+    }
+    return static_cast<T&>(*this);
+  }
+
+  T& setWill(const char* topic, uint8_t qos, bool retain, const char* payload) {
+    return setWill(topic, qos, retain, reinterpret_cast<const uint8_t*>(payload), strlen(payload));
+  }
+
+  T& setServer(IPAddress ip, uint16_t port) {
+    _ip = ip;
+    _port = port;
+    _useIp = true;
+    return static_cast<T&>(*this);
+  }
+
+  T& setServer(const char* host, uint16_t port) {
+    _host = host;
+    _port = port;
+    _useIp = false;
+    return static_cast<T&>(*this);
+  }
+
+  T& setTimeout(uint16_t timeout) {
+    _timeout = timeout * 1000;  // s to ms conversion, will also do 16 to 32 bit conversion
+    return static_cast<T&>(*this);
+  }
+
+  T& onConnect(espMqttClientTypes::OnConnectCallback callback) {
+    _onConnectCallback = callback;
+    return static_cast<T&>(*this);
+  }
+
+  T& onDisconnect(espMqttClientTypes::OnDisconnectCallback callback) {
+    _onDisconnectCallback = callback;
+    return static_cast<T&>(*this);
+  }
+
+  T& onSubscribe(espMqttClientTypes::OnSubscribeCallback callback) {
+    _onSubscribeCallback = callback;
+    return static_cast<T&>(*this);
+  }
+
+  T& onUnsubscribe(espMqttClientTypes::OnUnsubscribeCallback callback) {
+    _onUnsubscribeCallback = callback;
+    return static_cast<T&>(*this);
+  }
+
+  T& onMessage(espMqttClientTypes::OnMessageCallback callback) {
+    _onMessageCallback = callback;
+    return static_cast<T&>(*this);
+  }
+
+  T& onPublish(espMqttClientTypes::OnPublishCallback callback) {
+    _onPublishCallback = callback;
+    return static_cast<T&>(*this);
+  }
+
+  /*
+  T& onError(espMqttClientTypes::OnErrorCallback callback) {
+    _onErrorCallback = callback;
+    return static_cast<T&>(*this);
+  }
+  */
+
+ protected:
+  explicit MqttClientSetup(espMqttClientTypes::UseInternalTask useInternalTask, uint8_t priority = 1, uint8_t core = 1)
+  : MqttClient(useInternalTask, priority, core) {}
+};

lib/espMqttClient/src/Outbox.h

@@ -0,0 +1,207 @@
+
+/*
+Copyright (c) 2022 Bert Melis. All rights reserved.
+
+This work is licensed under the terms of the MIT license.  
+For a copy, see <https://opensource.org/licenses/MIT> or
+the LICENSE file.
+*/
+
+#pragma once
+
+#include <new>  // new (std::nothrow)
+#include <utility>  // std::forward
+
+namespace espMqttClientInternals {
+
+/**
+ * @brief Singly linked queue with builtin non-invalidating forward iterator
+ * 
+ * Queue items can only be emplaced, at front and back of the queue.
+ * Remove items using an iterator or the builtin iterator.
+ */
+
+template <typename T>
+class Outbox {
+ public:
+  Outbox()
+  : _first(nullptr)
+  , _last(nullptr)
+  , _current(nullptr)
+  , _prev(nullptr) {}
+  ~Outbox() {
+    while (_first) {
+      Node* n = _first->next;
+      delete _first;
+      _first = n;
+    }
+  }
+
+  struct Node {
+   public:
+    template <typename... Args>
+    explicit Node(Args&&... args)
+    : data(std::forward<Args>(args) ...)
+    , next(nullptr) {
+      // empty
+    }
+
+    T data;
+    Node* next;
+  };
+
+  class Iterator {
+    friend class Outbox;
+   public:
+    void operator++() {
+      if (_node) {
+        _prev = _node;
+        _node = _node->next;
+      }
+    }
+
+    explicit operator bool() const {
+      if (_node) return true;
+      return false;
+    }
+
+    T* get() const {
+      if (_node) return &(_node->data);
+      return nullptr;
+    }
+
+   private:
+    Node* _node = nullptr;
+    Node* _prev = nullptr;
+  };
+
+  // add node to back, advance current to new if applicable
+  template <class... Args>
+  Iterator emplace(Args&&... args) {
+    Iterator it;
+    Node* node = new (std::nothrow) Node(std::forward<Args>(args) ...);
+    if (node != nullptr) {
+      if (!_first) {
+        // queue is empty
+        _first = _current = node;
+      } else {
+        // queue has at least one item
+        _last->next = node;
+        it._prev = _last;
+      }
+      _last = node;
+      it._node = node;
+      // point current to newly created if applicable
+      if (!_current) {
+        _current = _last;
+      }
+    }
+    return it;
+  }
+
+  // add item to front, current points to newly created front.
+  template <class... Args>
+  Iterator emplaceFront(Args&&... args) {
+    Iterator it;
+    Node* node = new (std::nothrow) Node(std::forward<Args>(args) ...);
+    if (node != nullptr) {
+      if (!_first) {
+        // queue is empty
+        _last = node;
+      } else {
+        // queue has at least one item
+        node->next = _first;
+      }
+      _current = _first = node;
+      _prev = nullptr;
+      it._node = node;
+    }
+    return it;
+  }
+
+  // remove node at iterator, iterator points to next
+  void remove(Iterator& it) {  // NOLINT(runtime/references)
+    if (!it) return;
+    Node* node = it._node;
+    Node* prev = it._prev;
+    ++it;
+    _remove(prev, node);
+  }
+
+  // remove current node, current points to next
+  void removeCurrent() {
+    _remove(_prev, _current);
+  }
+
+  // Get current item or return nullptr
+  T* getCurrent() const {
+    if (_current) return &(_current->data);
+    return nullptr;
+  }
+
+  void resetCurrent() {
+    _current = _first;
+  }
+
+  Iterator front() const {
+    Iterator it;
+    it._node = _first;
+    return it;
+  }
+
+  // Advance current item
+  void next() {
+    if (_current) {
+      _prev = _current;
+      _current = _current->next;
+    }
+  }
+
+  // Outbox is empty
+  bool empty() {
+    if (!_first) return true;
+    return false;
+  }
+
+ private:
+  Node* _first;
+  Node* _last;
+  Node* _current;
+  Node* _prev;  // element just before _current
+
+  void _remove(Node* prev, Node* node) {
+    if (!node) return;
+
+    // set current to next, node->next may be nullptr
+    if (_current == node) {
+      _current = node->next;
+    }
+
+    if (_prev == node) {
+      _prev = prev;
+    }
+
+    // only one element in outbox
+    if (_first == _last) {
+      _first = _last = nullptr;
+
+    // delete first el in longer outbox
+    } else if (_first == node) {
+      _first = node->next;
+
+    // delete last in longer outbox
+    } else if (_last == node) {
+      _last = prev;
+      _last->next = nullptr;
+
+    // delete somewhere in the middle
+    } else {
+      prev->next = node->next;
+    }
+
+    // finally, delete the node
+    delete node;
+  }
+};
+
+}  // end namespace espMqttClientInternals

lib/espMqttClient/src/Packets/Constants.h

@@ -0,0 +1,77 @@
+/*
+Copyright (c) 2022 Bert Melis. All rights reserved.
+
+Parts are based on the original work of Marvin Roger:
+https://github.com/marvinroger/async-mqtt-client
+
+This work is licensed under the terms of the MIT license.  
+For a copy, see <https://opensource.org/licenses/MIT> or
+the LICENSE file.
+*/
+
+#pragma once
+
+#include <stdint.h>
+
+namespace espMqttClientInternals {
+
+constexpr const char PROTOCOL[] = "MQTT";
+constexpr const uint8_t PROTOCOL_LEVEL = 0b00000100;
+
+typedef uint8_t MQTTPacketType;
+
+constexpr struct {
+  const uint8_t RESERVED1   = 0;
+  const uint8_t CONNECT     = 1 << 4;
+  const uint8_t CONNACK     = 2 << 4;
+  const uint8_t PUBLISH     = 3 << 4;
+  const uint8_t PUBACK      = 4 << 4;
+  const uint8_t PUBREC      = 5 << 4;
+  const uint8_t PUBREL      = 6 << 4;
+  const uint8_t PUBCOMP     = 7 << 4;
+  const uint8_t SUBSCRIBE   = 8 << 4;
+  const uint8_t SUBACK      = 9 << 4;
+  const uint8_t UNSUBSCRIBE = 10 << 4;
+  const uint8_t UNSUBACK    = 11 << 4;
+  const uint8_t PINGREQ     = 12 << 4;
+  const uint8_t PINGRESP    = 13 << 4;
+  const uint8_t DISCONNECT  = 14 << 4;
+  const uint8_t RESERVED2   = 1 << 4;
+} PacketType;
+
+constexpr struct {
+  const uint8_t CONNECT_RESERVED     = 0x00;
+  const uint8_t CONNACK_RESERVED     = 0x00;
+  const uint8_t PUBLISH_DUP          = 0x08;
+  const uint8_t PUBLISH_QOS0         = 0x00;
+  const uint8_t PUBLISH_QOS1         = 0x02;
+  const uint8_t PUBLISH_QOS2         = 0x04;
+  const uint8_t PUBLISH_QOSRESERVED  = 0x06;
+  const uint8_t PUBLISH_RETAIN       = 0x01;
+  const uint8_t PUBACK_RESERVED      = 0x00;
+  const uint8_t PUBREC_RESERVED      = 0x00;
+  const uint8_t PUBREL_RESERVED      = 0x02;
+  const uint8_t PUBCOMP_RESERVED     = 0x00;
+  const uint8_t SUBSCRIBE_RESERVED   = 0x02;
+  const uint8_t SUBACK_RESERVED      = 0x00;
+  const uint8_t UNSUBSCRIBE_RESERVED = 0x02;
+  const uint8_t UNSUBACK_RESERVED    = 0x00;
+  const uint8_t PINGREQ_RESERVED     = 0x00;
+  const uint8_t PINGRESP_RESERVED    = 0x00;
+  const uint8_t DISCONNECT_RESERVED  = 0x00;
+  const uint8_t RESERVED2_RESERVED   = 0x00;
+} HeaderFlag;
+
+constexpr struct {
+  const uint8_t USERNAME      = 0x80;
+  const uint8_t PASSWORD      = 0x40;
+  const uint8_t WILL_RETAIN   = 0x20;
+  const uint8_t WILL_QOS0     = 0x00;
+  const uint8_t WILL_QOS1     = 0x08;
+  const uint8_t WILL_QOS2     = 0x10;
+  const uint8_t WILL          = 0x04;
+  const uint8_t CLEAN_SESSION = 0x02;
+  const uint8_t RESERVED      = 0x00;
+} ConnectFlag;
+
+}  // end namespace espMqttClientInternals

lib/espMqttClient/src/Packets/Packet.cpp

@@ -0,0 +1,438 @@
+/*
+Copyright (c) 2022 Bert Melis. All rights reserved.
+
+This work is licensed under the terms of the MIT license.  
+For a copy, see <https://opensource.org/licenses/MIT> or
+the LICENSE file.
+*/
+
+#include "Packet.h"
+
+namespace espMqttClientInternals {
+
+Packet::~Packet() {
+  free(_data);
+}
+
+size_t Packet::available(size_t index) {
+  if (index >= _size) return 0;
+  if (!_getPayload) return _size - index;
+  return _chunkedAvailable(index);
+}
+
+const uint8_t* Packet::data(size_t index) const {
+  if (!_getPayload) {
+    if (!_data) return nullptr;
+    if (index >= _size) return nullptr;
+    return &_data[index];
+  }
+  return _chunkedData(index);
+}
+
+size_t Packet::size() const {
+  return _size;
+}
+
+void Packet::setDup() {
+  if (!_data) return;
+  if (packetType() != PacketType.PUBLISH) return;
+  if (_packetId == 0) return;
+  _data[0] |= 0x08;
+}
+
+uint16_t Packet::packetId() const {
+  return _packetId;
+}
+
+MQTTPacketType Packet::packetType() const {
+  if (_data) return static_cast<MQTTPacketType>(_data[0] & 0xF0);
+  return static_cast<MQTTPacketType>(0);
+}
+
+bool Packet::removable() const {
+  if (_packetId == 0) return true;
+  if ((packetType() == PacketType.PUBACK) || (packetType() == PacketType.PUBCOMP)) return true;
+  return false;
+}
+
+Packet::Packet(espMqttClientTypes::Error& error,
+               bool cleanSession,
+               const char* username,
+               const char* password,
+               const char* willTopic,
+               bool willRetain,
+               uint8_t willQos,
+               const uint8_t* willPayload,
+               uint16_t willPayloadLength,
+               uint16_t keepAlive,
+               const char* clientId)
+: _packetId(0)
+, _data(nullptr)
+, _size(0)
+, _payloadIndex(0)
+, _payloadStartIndex(0)
+, _payloadEndIndex(0)
+, _getPayload(nullptr) {
+  if (willPayload && willPayloadLength == 0) {
+    size_t length = strlen(reinterpret_cast<const char*>(willPayload));
+    if (length > UINT16_MAX) {
+      emc_log_w("Payload length truncated (l:%zu)", length);
+      willPayloadLength = UINT16_MAX;
+    } else {
+      willPayloadLength = length;
+    }
+  }
+  if (!clientId || strlen(clientId) == 0) {
+    emc_log_w("clientId not set error");
+    error = espMqttClientTypes::Error::MALFORMED_PARAMETER;
+    return;
+  }
+
+  // Calculate size
+  size_t remainingLength =
+  6 +  // protocol
+  1 +  // protocol level
+  1 +  // connect flags
+  2 +  // keepalive
+  2 + strlen(clientId) +
+  (willTopic ? 2 + strlen(willTopic) + 2 + willPayloadLength : 0) +
+  (username ? 2 + strlen(username) : 0) +
+  (password ? 2 + strlen(password) : 0);
+
+  // allocate memory
+  if (!_allocate(remainingLength)) {
+    error = espMqttClientTypes::Error::OUT_OF_MEMORY;
+    return;
+  }
+
+  // serialize
+  size_t pos = 0;
+
+  // FIXED HEADER
+  _data[pos++] = PacketType.CONNECT | HeaderFlag.CONNECT_RESERVED;
+  pos += encodeRemainingLength(remainingLength, &_data[pos]);
+  pos += encodeString(PROTOCOL, &_data[pos]);
+  _data[pos++] = PROTOCOL_LEVEL;
+  uint8_t connectFlags = 0;
+  if (cleanSession) connectFlags |= espMqttClientInternals::ConnectFlag.CLEAN_SESSION;
+  if (username != nullptr) connectFlags |= espMqttClientInternals::ConnectFlag.USERNAME;
+  if (password != nullptr) connectFlags |= espMqttClientInternals::ConnectFlag.PASSWORD;
+  if (willTopic != nullptr) {
+    connectFlags |= espMqttClientInternals::ConnectFlag.WILL;
+    if (willRetain) connectFlags |= espMqttClientInternals::ConnectFlag.WILL_RETAIN;
+    switch (willQos) {
+      case 0:
+        connectFlags |= espMqttClientInternals::ConnectFlag.WILL_QOS0;
+        break;
+      case 1:
+        connectFlags |= espMqttClientInternals::ConnectFlag.WILL_QOS1;
+        break;
+      case 2:
+        connectFlags |= espMqttClientInternals::ConnectFlag.WILL_QOS2;
+        break;
+    }
+  }
+  _data[pos++] = connectFlags;
+  _data[pos++] = keepAlive >> 8;
+  _data[pos++] = keepAlive & 0xFF;
+
+  // PAYLOAD
+  // client ID
+  pos += encodeString(clientId, &_data[pos]);
+  // will
+  if (willTopic != nullptr && willPayload != nullptr) {
+    pos += encodeString(willTopic, &_data[pos]);
+    _data[pos++] = willPayloadLength >> 8;
+    _data[pos++] = willPayloadLength & 0xFF;
+    memcpy(&_data[pos], willPayload, willPayloadLength);
+    pos += willPayloadLength;
+  }
+  // credentials
+  if (username != nullptr) pos += encodeString(username, &_data[pos]);
+  if (password != nullptr) encodeString(password, &_data[pos]);
+
+  error = espMqttClientTypes::Error::SUCCESS;
+}
+
+Packet::Packet(espMqttClientTypes::Error& error,
+               uint16_t packetId,
+               const char* topic,
+               const uint8_t* payload,
+               size_t payloadLength,
+               uint8_t qos,
+               bool retain)
+: _packetId(packetId)
+, _data(nullptr)
+, _size(0)
+, _payloadIndex(0)
+, _payloadStartIndex(0)
+, _payloadEndIndex(0)
+, _getPayload(nullptr) {
+  size_t remainingLength =
+    2 + strlen(topic) +  // topic length + topic
+    2 +                  // packet ID
+    payloadLength;
+
+  if (qos == 0) {
+    remainingLength -= 2;
+    _packetId = 0;
+  }
+
+  if (!_allocate(remainingLength)) {
+    error = espMqttClientTypes::Error::OUT_OF_MEMORY;
+    return;
+  }
+
+  size_t pos = _fillPublishHeader(packetId, topic, remainingLength, qos, retain);
+
+  // PAYLOAD
+  memcpy(&_data[pos], payload, payloadLength);
+
+  error = espMqttClientTypes::Error::SUCCESS;
+}
+
+Packet::Packet(espMqttClientTypes::Error& error,
+               uint16_t packetId,
+               const char* topic,
+               espMqttClientTypes::PayloadCallback payloadCallback,
+               size_t payloadLength,
+               uint8_t qos,
+               bool retain)
+: _packetId(packetId)
+, _data(nullptr)
+, _size(0)
+, _payloadIndex(0)
+, _payloadStartIndex(0)
+, _payloadEndIndex(0)
+, _getPayload(payloadCallback) {
+  size_t remainingLength =
+    2 + strlen(topic) +  // topic length + topic
+    2 +                  // packet ID
+    payloadLength;
+
+  if (qos == 0) {
+    remainingLength -= 2;
+    _packetId = 0;
+  }
+
+  if (!_allocate(remainingLength - payloadLength + std::min(payloadLength, static_cast<size_t>(EMC_RX_BUFFER_SIZE)))) {
+    error = espMqttClientTypes::Error::OUT_OF_MEMORY;
+    return;
+  }
+
+  size_t pos = _fillPublishHeader(packetId, topic, remainingLength, qos, retain);
+
+  // payload will be added by 'Packet::available'
+  _size = pos + payloadLength;
+  _payloadIndex = pos;
+  _payloadStartIndex = _payloadIndex;
+  _payloadEndIndex = _payloadIndex;
+
+  error = espMqttClientTypes::Error::SUCCESS;
+}
+
+Packet::Packet(espMqttClientTypes::Error& error, uint16_t packetId, const char* topic, uint8_t qos)
+: _packetId(packetId)
+, _data(nullptr)
+, _size(0)
+, _payloadIndex(0)
+, _payloadStartIndex(0)
+, _payloadEndIndex(0)
+, _getPayload(nullptr) {
+  SubscribeItem list[1] = {topic, qos};
+  _createSubscribe(error, list, 1);
+}
+
+Packet::Packet(espMqttClientTypes::Error& error, MQTTPacketType type, uint16_t packetId)
+: _packetId(packetId)
+, _data(nullptr)
+, _size(0)
+, _payloadIndex(0)
+, _payloadStartIndex(0)
+, _payloadEndIndex(0)
+, _getPayload(nullptr) {
+  if (!_allocate(2)) {
+    error = espMqttClientTypes::Error::OUT_OF_MEMORY;
+    return;
+  }
+
+  size_t pos = 0;
+  _data[pos] = type;
+  if (type == PacketType.PUBREL) {
+    _data[pos++] |= HeaderFlag.PUBREL_RESERVED;
+  } else {
+    pos++;
+  }
+  pos += encodeRemainingLength(2, &_data[pos]);
+  _data[pos++] = packetId >> 8;
+  _data[pos] = packetId & 0xFF;
+
+  error = espMqttClientTypes::Error::SUCCESS;
+}
+
+Packet::Packet(espMqttClientTypes::Error& error, uint16_t packetId, const char* topic)
+: _packetId(packetId)
+, _data(nullptr)
+, _size(0)
+, _payloadIndex(0)
+, _payloadStartIndex(0)
+, _payloadEndIndex(0)
+, _getPayload(nullptr) {
+  const char* list[1] = {topic};
+  _createUnsubscribe(error, list, 1);
+}
+
+Packet::Packet(espMqttClientTypes::Error& error, MQTTPacketType type)
+: _packetId(0)
+, _data(nullptr)
+, _size(0)
+, _payloadIndex(0)
+, _payloadStartIndex(0)
+, _payloadEndIndex(0)
+, _getPayload(nullptr) {
+  if (!_allocate(0)) {
+    error = espMqttClientTypes::Error::OUT_OF_MEMORY;
+    return;
+  }
+  _data[0] |= type;
+
+  error = espMqttClientTypes::Error::SUCCESS;
+}
+
+
+bool Packet::_allocate(size_t remainingLength) {
+  if (EMC_GET_FREE_MEMORY() < EMC_MIN_FREE_MEMORY) {
+    emc_log_w("Packet buffer not allocated: low memory");
+    return false;
+  }
+  _size = 1 + remainingLengthLength(remainingLength) + remainingLength;
+  _data = reinterpret_cast<uint8_t*>(malloc(_size));
+  if (!_data) {
+    _size = 0;
+    emc_log_w("Alloc failed (l:%zu)", _size);
+    return false;
+  }
+  emc_log_i("Alloc (l:%zu)", _size);
+  memset(_data, 0, _size);
+  return true;
+}
+
+size_t Packet::_fillPublishHeader(uint16_t packetId,
+                                  const char* topic,
+                                  size_t remainingLength,
+                                  uint8_t qos,
+                                  bool retain) {
+  size_t index = 0;
+
+  // FIXED HEADER
+  _data[index] = PacketType.PUBLISH;
+  if (retain) _data[index] |= HeaderFlag.PUBLISH_RETAIN;
+  if (qos == 0) {
+    _data[index++] |= HeaderFlag.PUBLISH_QOS0;
+  } else if (qos == 1) {
+    _data[index++] |= HeaderFlag.PUBLISH_QOS1;
+  } else if (qos == 2) {
+    _data[index++] |= HeaderFlag.PUBLISH_QOS2;
+  }
+  index += encodeRemainingLength(remainingLength, &_data[index]);
+
+  // VARIABLE HEADER
+  index += encodeString(topic, &_data[index]);
+  if (qos > 0) {
+    _data[index++] = packetId >> 8;
+    _data[index++] = packetId & 0xFF;
+  }
+
+  return index;
+}
+
+void Packet::_createSubscribe(espMqttClientTypes::Error& error,
+                              SubscribeItem* list,
+                              size_t numberTopics) {
+  // Calculate size
+  size_t payload = 0;
+  for (size_t i = 0; i < numberTopics; ++i) {
+    payload += 2 + strlen(list[i].topic) + 1;  // length bytes, string, qos
+  }
+  size_t remainingLength = 2 + payload;  // packetId + payload
+
+  // allocate memory
+  if (!_allocate(remainingLength)) {
+    error = espMqttClientTypes::Error::OUT_OF_MEMORY;
+    return;
+  }
+
+  // serialize
+  size_t pos = 0;
+  _data[pos++] = PacketType.SUBSCRIBE | HeaderFlag.SUBSCRIBE_RESERVED;
+  pos += encodeRemainingLength(remainingLength, &_data[pos]);
+  _data[pos++] = _packetId >> 8;
+  _data[pos++] = _packetId & 0xFF;
+  for (size_t i = 0; i < numberTopics; ++i) {
+    pos += encodeString(list[i].topic, &_data[pos]);
+    _data[pos++] = list[i].qos;
+  }
+
+  error = espMqttClientTypes::Error::SUCCESS;
+}
+
+void Packet::_createUnsubscribe(espMqttClientTypes::Error& error,
+                                const char** list,
+                                size_t numberTopics) {
+  // Calculate size
+  size_t payload = 0;
+  for (size_t i = 0; i < numberTopics; ++i) {
+    payload += 2 + strlen(list[i]);  // length bytes, string
+  }
+  size_t remainingLength = 2 + payload;  // packetId + payload
+
+  // allocate memory
+  if (!_allocate(remainingLength)) {
+    error = espMqttClientTypes::Error::OUT_OF_MEMORY;
+    return;
+  }
+
+  // serialize
+  size_t pos = 0;
+  _data[pos++] = PacketType.UNSUBSCRIBE | HeaderFlag.UNSUBSCRIBE_RESERVED;
+  pos += encodeRemainingLength(remainingLength, &_data[pos]);
+  _data[pos++] = _packetId >> 8;
+  _data[pos++] = _packetId & 0xFF;
+  for (size_t i = 0; i < numberTopics; ++i) {
+    pos += encodeString(list[i], &_data[pos]);
+  }
+
+  error = espMqttClientTypes::Error::SUCCESS;
+}
+
+size_t Packet::_chunkedAvailable(size_t index) {
+  // index vs size check done in 'available(index)'
+
+  // index points to header or first payload byte
+  if (index < _payloadIndex) {
+    if (_size > _payloadIndex && _payloadEndIndex != 0) {
+      size_t copied = _getPayload(&_data[_payloadIndex], std::min(static_cast<size_t>(EMC_TX_BUFFER_SIZE), _size - _payloadStartIndex), index);
+      _payloadStartIndex = _payloadIndex;
+      _payloadEndIndex = _payloadStartIndex + copied - 1;
+    }
+
+  // index points to payload unavailable
+  } else if (index > _payloadEndIndex || _payloadStartIndex > index) {
+    _payloadStartIndex = index;
+    size_t copied = _getPayload(&_data[_payloadIndex], std::min(static_cast<size_t>(EMC_TX_BUFFER_SIZE), _size - _payloadStartIndex), index);
+    _payloadEndIndex = _payloadStartIndex + copied - 1;
+  }
+
+  // now index points to header or payload available
+  return _payloadEndIndex - index + 1;
+}
+
+const uint8_t* Packet::_chunkedData(size_t index) const {
+  // CAUTION!! available(index) has to be called first to check available data and possibly fill payloadbuffer
+  if (index < _payloadIndex) {
+    return &_data[index];
+  }
+  return &_data[index - _payloadStartIndex + _payloadIndex];
+}
+
+}  // end namespace espMqttClientInternals

lib/espMqttClient/src/Packets/Packet.h

@@ -0,0 +1,155 @@
+/*
+Copyright (c) 2022 Bert Melis. All rights reserved.
+
+This work is licensed under the terms of the MIT license.  
+For a copy, see <https://opensource.org/licenses/MIT> or
+the LICENSE file.
+*/
+
+#pragma once
+
+#include <stdint.h>
+#include <stddef.h>
+
+#include "Constants.h"
+#include "../Config.h"
+#include "../TypeDefs.h"
+#include "../Helpers.h"
+#include "../Logging.h"
+#include "RemainingLength.h"
+#include "String.h"
+
+namespace espMqttClientInternals {
+
+class Packet {
+ public:
+  ~Packet();
+  size_t available(size_t index);
+  const uint8_t* data(size_t index) const;
+
+  size_t size() const;
+  void setDup();
+  uint16_t packetId() const;
+  MQTTPacketType packetType() const;
+  bool removable() const;
+
+ protected:
+  uint16_t _packetId;  // save as separate variable: will be accessed frequently
+  uint8_t* _data;
+  size_t _size;
+
+  // variables for chunked payload handling
+  size_t _payloadIndex;
+  size_t _payloadStartIndex;
+  size_t _payloadEndIndex;
+  espMqttClientTypes::PayloadCallback _getPayload;
+
+  struct SubscribeItem {
+    const char* topic;
+    uint8_t qos;
+  };
+
+ public:
+  // CONNECT
+  Packet(espMqttClientTypes::Error& error,  // NOLINT(runtime/references)
+         bool cleanSession,
+         const char* username,
+         const char* password,
+         const char* willTopic,
+         bool willRetain,
+         uint8_t willQos,
+         const uint8_t* willPayload,
+         uint16_t willPayloadLength,
+         uint16_t keepAlive,
+         const char* clientId);
+  // PUBLISH
+  Packet(espMqttClientTypes::Error& error,  // NOLINT(runtime/references)
+         uint16_t packetId,
+         const char* topic,
+         const uint8_t* payload,
+         size_t payloadLength,
+         uint8_t qos,
+         bool retain);
+  Packet(espMqttClientTypes::Error& error,  // NOLINT(runtime/references)
+         uint16_t packetId,
+         const char* topic,
+         espMqttClientTypes::PayloadCallback payloadCallback,
+         size_t payloadLength,
+         uint8_t qos,
+         bool retain);
+  // SUBSCRIBE
+  Packet(espMqttClientTypes::Error& error,  // NOLINT(runtime/references)
+         uint16_t packetId,
+         const char* topic,
+         uint8_t qos);
+  template<typename ... Args>
+  Packet(espMqttClientTypes::Error& error,  // NOLINT(runtime/references)
+         uint16_t packetId,
+         const char* topic1,
+         uint8_t qos1,
+         const char* topic2,
+         uint8_t qos2,
+         Args&& ... args)
+  : _packetId(packetId)
+  , _data(nullptr)
+  , _size(0)
+  , _payloadIndex(0)
+  , _payloadStartIndex(0)
+  , _payloadEndIndex(0)
+  , _getPayload(nullptr) {
+    static_assert(sizeof...(Args) % 2 == 0, "Subscribe should be in topic/qos pairs");
+    size_t numberTopics = 2 + (sizeof...(Args) / 2);
+    SubscribeItem list[numberTopics] = {topic1, qos1, topic2, qos2, args...};
+    _createSubscribe(error, list, numberTopics);
+  }
+  // UNSUBSCRIBE
+  Packet(espMqttClientTypes::Error& error,  // NOLINT(runtime/references)
+         uint16_t packetId,
+         const char* topic);
+  template<typename ... Args>
+  Packet(espMqttClientTypes::Error& error,  // NOLINT(runtime/references)
+         uint16_t packetId,
+         const char* topic1,
+         const char* topic2,
+         Args&& ... args)
+  : _packetId(packetId)
+  , _data(nullptr)
+  , _size(0)
+  , _payloadIndex(0)
+  , _payloadStartIndex(0)
+  , _payloadEndIndex(0)
+  , _getPayload(nullptr) {
+    size_t numberTopics = 2 + sizeof...(Args);
+    const char* list[numberTopics] = {topic1, topic2, args...};
+    _createUnsubscribe(error, list, numberTopics);
+  }
+  // PUBACK, PUBREC, PUBREL, PUBCOMP
+  Packet(espMqttClientTypes::Error& error,  // NOLINT(runtime/references)
+         MQTTPacketType type,
+         uint16_t packetId);
+  // PING, DISCONN
+  explicit Packet(espMqttClientTypes::Error& error,  // NOLINT(runtime/references)
+                  MQTTPacketType type);
+
+ private:
+  // pass remainingLength = total size - header - remainingLengthLength!
+  bool _allocate(size_t remainingLength);
+
+  // fills header and returns index of next available byte in buffer
+  size_t _fillPublishHeader(uint16_t packetId,
+                            const char* topic,
+                            size_t remainingLength,
+                            uint8_t qos,
+                            bool retain);
+  void _createSubscribe(espMqttClientTypes::Error& error,  // NOLINT(runtime/references)
+                        SubscribeItem* list,
+                        size_t numberTopics);
+  void _createUnsubscribe(espMqttClientTypes::Error& error,  // NOLINT(runtime/references)
+                          const char** list,
+                          size_t numberTopics);
+
+  size_t _chunkedAvailable(size_t index);
+  const uint8_t* _chunkedData(size_t index) const;
+};
+
+}  // end namespace espMqttClientInternals

lib/espMqttClient/src/Packets/Parser.cpp

@@ -0,0 +1,316 @@
+/*
+Copyright (c) 2022 Bert Melis. All rights reserved.
+
+This work is licensed under the terms of the MIT license.  
+For a copy, see <https://opensource.org/licenses/MIT> or
+the LICENSE file.
+*/
+
+#include "Parser.h"
+
+namespace espMqttClientInternals {
+
+uint8_t IncomingPacket::qos() const {
+  if ((fixedHeader.packetType & 0xF0) != PacketType.PUBLISH) return 0;
+  return (fixedHeader.packetType & 0x06) >> 1;  // mask 0x00000110
+}
+
+bool IncomingPacket::retain() const {
+  if ((fixedHeader.packetType & 0xF0) != PacketType.PUBLISH) return 0;
+  return fixedHeader.packetType & 0x01;  // mask 0x00000001
+}
+
+bool IncomingPacket::dup() const {
+  if ((fixedHeader.packetType & 0xF0) != PacketType.PUBLISH) return 0;
+  return fixedHeader.packetType & 0x08;  // mask 0x00001000
+}
+
+void IncomingPacket::reset() {
+  fixedHeader.packetType = 0;
+  variableHeader.topicLength = 0;
+  variableHeader.fixed.packetId = 0;
+  payload.index = 0;
+  payload.length = 0;
+}
+
+Parser::Parser()
+: _data(nullptr)
+, _len(0)
+, _bytesRead(0)
+, _bytePos(0)
+, _parse(_fixedHeader)
+, _packet()
+, _payloadBuffer{0} {
+  // empty
+}
+
+ParserResult Parser::parse(const uint8_t* data, size_t len, size_t* bytesRead) {
+  _data = data;
+  _len = len;
+  _bytesRead = 0;
+  ParserResult result = ParserResult::awaitData;
+  while (result == ParserResult::awaitData && _bytesRead < _len) {
+    result = _parse(this);
+    ++_bytesRead;
+  }
+  (*bytesRead) += _bytesRead;
+  return result;
+}
+
+const IncomingPacket& Parser::getPacket() const {
+  return _packet;
+}
+
+void Parser::reset() {
+  _parse = _fixedHeader;
+  _bytesRead = 0;
+  _bytePos = 0;
+  _packet.reset();
+}
+
+ParserResult Parser::_fixedHeader(Parser* p) {
+  p->_packet.reset();
+  p->_packet.fixedHeader.packetType = p->_data[p->_bytesRead];
+
+  // keep PUBLISH out of the switch and handle in separate if/else
+  if ((p->_packet.fixedHeader.packetType & 0xF0) == PacketType.PUBLISH) {
+    uint8_t headerFlags = p->_packet.fixedHeader.packetType & 0x0F;
+    /* flags can be: 0b0000 --> no dup, qos 0, no retain
+                     0x0001 --> no dup, qos 0, retain
+                     0x0010 --> no dup, qos 1, no retain
+                     0x0011 --> no dup, qos 1, retain
+                     0x0100 --> no dup, qos 2, no retain
+                     0x0101 --> no dup, qos 2, retain
+                     0x1010 --> dup, qos 1, no retain
+                     0x1011 --> dup, qos 1, retain
+                     0x1100 --> dup, qos 2, no retain
+                     0x1101 --> dup, qos 2, retain
+    */
+    if (headerFlags <= 0x05 || headerFlags >= 0x0A) {
+      p->_parse = _remainingLengthVariable;
+      p->_bytePos = 0;
+    } else {
+      emc_log_w("Invalid packet header: 0x%02x", p->_packet.fixedHeader.packetType);
+      return ParserResult::protocolError;
+    }
+  } else {
+    switch (p->_packet.fixedHeader.packetType) {
+      case PacketType.CONNACK | HeaderFlag.CONNACK_RESERVED:
+      case PacketType.PUBACK | HeaderFlag.PUBACK_RESERVED:
+      case PacketType.PUBREC | HeaderFlag.PUBREC_RESERVED:
+      case PacketType.PUBREL | HeaderFlag.PUBREL_RESERVED:
+      case PacketType.PUBCOMP | HeaderFlag.PUBCOMP_RESERVED:
+      case PacketType.UNSUBACK | HeaderFlag.UNSUBACK_RESERVED:
+        p->_parse = _remainingLengthFixed;
+        break;
+      case PacketType.SUBACK | HeaderFlag.SUBACK_RESERVED:
+        p->_parse = _remainingLengthVariable;
+        p->_bytePos = 0;
+        break;
+      case PacketType.PINGRESP | HeaderFlag.PINGRESP_RESERVED:
+        p->_parse = _remainingLengthNone;
+        break;
+      default:
+        emc_log_w("Invalid packet header: 0x%02x", p->_packet.fixedHeader.packetType);
+        return ParserResult::protocolError;
+    }
+  }
+  emc_log_i("Packet type: 0x%02x", p->_packet.fixedHeader.packetType);
+  return ParserResult::awaitData;
+}
+
+ParserResult Parser::_remainingLengthFixed(Parser* p) {
+  p->_packet.fixedHeader.remainingLength.remainingLength = p->_data[p->_bytesRead];
+
+  if (p->_packet.fixedHeader.remainingLength.remainingLength == 2) {  // variable header is 2 bytes long
+    if ((p->_packet.fixedHeader.packetType & 0xF0) != PacketType.CONNACK) {
+      p->_parse = _varHeaderPacketId1;
+    } else {
+      p->_parse = _varHeaderConnack1;
+    }
+    emc_log_i("Remaining length: %zu", p->_packet.fixedHeader.remainingLength.remainingLength);
+    return ParserResult::awaitData;
+  }
+  p->_parse = _fixedHeader;
+  emc_log_w("Invalid remaining length (fixed): %zu",  p->_packet.fixedHeader.remainingLength.remainingLength);
+  return ParserResult::protocolError;
+}
+
+ParserResult Parser::_remainingLengthVariable(Parser* p) {
+  p->_packet.fixedHeader.remainingLength.remainingLengthRaw[p->_bytePos] = p->_data[p->_bytesRead];
+  if (p->_packet.fixedHeader.remainingLength.remainingLengthRaw[p->_bytePos] & 0x80) {
+    p->_bytePos++;
+    if (p->_bytePos == 4) {
+      emc_log_w("Invalid remaining length (variable)");
+      return ParserResult::protocolError;
+    } else {
+      return ParserResult::awaitData;
+    }
+  }
+
+  // no need to check for negative decoded length, check is already done
+  p->_packet.fixedHeader.remainingLength.remainingLength = decodeRemainingLength(p->_packet.fixedHeader.remainingLength.remainingLengthRaw);
+
+  if ((p->_packet.fixedHeader.packetType & 0xF0) == PacketType.PUBLISH) {
+    p->_parse = _varHeaderTopicLength1;
+    emc_log_i("Remaining length: %zu", p->_packet.fixedHeader.remainingLength.remainingLength);
+    return ParserResult::awaitData;
+  } else {
+    int32_t payloadSize = p->_packet.fixedHeader.remainingLength.remainingLength - 2;  // total - packet ID
+    if (0 < payloadSize && payloadSize < EMC_PAYLOAD_BUFFER_SIZE) {
+      p->_bytePos = 0;
+      p->_packet.payload.data = p->_payloadBuffer;
+      p->_packet.payload.index = 0;
+      p->_packet.payload.length = payloadSize;
+      p->_packet.payload.total = payloadSize;
+      p->_parse = _varHeaderPacketId1;
+      emc_log_i("Remaining length: %zu", p->_packet.fixedHeader.remainingLength.remainingLength);
+      return ParserResult::awaitData;
+    } else {
+      emc_log_w("Invalid payload length");
+    }
+  }
+  p->_parse = _fixedHeader;
+  return ParserResult::protocolError;
+}
+
+ParserResult Parser::_remainingLengthNone(Parser* p) {
+  p->_packet.fixedHeader.remainingLength.remainingLength = p->_data[p->_bytesRead];
+  p->_parse = _fixedHeader;
+  if (p->_packet.fixedHeader.remainingLength.remainingLength == 0) {
+    emc_log_i("Remaining length: %zu", p->_packet.fixedHeader.remainingLength.remainingLength);
+    return ParserResult::packet;
+  }
+  emc_log_w("Invalid remaining length (none)");
+  return ParserResult::protocolError;
+}
+
+ParserResult Parser::_varHeaderConnack1(Parser* p) {
+  uint8_t data = p->_data[p->_bytesRead];
+  if (data < 2) {  // session present flag: equal to 0 or 1
+    p->_packet.variableHeader.fixed.connackVarHeader.sessionPresent = data;
+    p->_parse = _varHeaderConnack2;
+    return ParserResult::awaitData;
+  }
+  p->_parse = _fixedHeader;
+  emc_log_w("Invalid session flags");
+  return ParserResult::protocolError;
+}
+
+ParserResult Parser::_varHeaderConnack2(Parser* p) {
+  uint8_t data = p->_data[p->_bytesRead];
+  p->_parse = _fixedHeader;
+  if (data <= 5) {  // connect return code max is 5
+    p->_packet.variableHeader.fixed.connackVarHeader.returnCode = data;
+    emc_log_i("Packet complete");
+    return ParserResult::packet;
+  }
+  emc_log_w("Invalid connack return code");
+  return ParserResult::protocolError;
+}
+
+ParserResult Parser::_varHeaderPacketId1(Parser* p) {
+  p->_packet.variableHeader.fixed.packetId |= p->_data[p->_bytesRead] << 8;
+  p->_parse = _varHeaderPacketId2;
+  return ParserResult::awaitData;
+}
+
+ParserResult Parser::_varHeaderPacketId2(Parser* p) {
+  p->_packet.variableHeader.fixed.packetId |= p->_data[p->_bytesRead];
+  p->_parse = _fixedHeader;
+  if (p->_packet.variableHeader.fixed.packetId != 0) {
+    emc_log_i("Packet variable header complete");
+    if ((p->_packet.fixedHeader.packetType & 0xF0) == PacketType.SUBACK) {
+      p->_parse = _payloadSuback;
+      return ParserResult::awaitData;
+    } else if ((p->_packet.fixedHeader.packetType & 0xF0) == PacketType.PUBLISH) {
+      p->_packet.payload.total -= 2;  // substract packet id length from payload
+      if (p->_packet.payload.total == 0) {
+        p->_parse = _fixedHeader;
+        return ParserResult::packet;
+      } else {
+        p->_parse = _payloadPublish;
+      }
+      return ParserResult::awaitData;
+    } else {
+      return ParserResult::packet;
+    }
+  } else {
+    emc_log_w("Invalid packet id");
+    return ParserResult::protocolError;
+  }
+}
+
+ParserResult Parser::_varHeaderTopicLength1(Parser* p) {
+  p->_packet.variableHeader.topicLength = p->_data[p->_bytesRead] << 8;
+  p->_parse = _varHeaderTopicLength2;
+  return ParserResult::awaitData;
+}
+
+ParserResult Parser::_varHeaderTopicLength2(Parser* p) {
+  p->_packet.variableHeader.topicLength |= p->_data[p->_bytesRead];
+  size_t maxTopicLength =
+    p->_packet.fixedHeader.remainingLength.remainingLength
+    - 2  // topic length bytes
+    - ((p->_packet.fixedHeader.packetType & (HeaderFlag.PUBLISH_QOS1 | HeaderFlag.PUBLISH_QOS2)) ? 2 : 0);
+  if (p->_packet.variableHeader.topicLength <= maxTopicLength) {
+    p->_parse = _varHeaderTopic;
+    p->_bytePos = 0;
+    p->_packet.payload.total = p->_packet.fixedHeader.remainingLength.remainingLength - 2 - p->_packet.variableHeader.topicLength;
+    return ParserResult::awaitData;
+  }
+  emc_log_w("Invalid topic length: %u > %zu", p->_packet.variableHeader.topicLength, maxTopicLength);
+  p->_parse = _fixedHeader;
+  return ParserResult::protocolError;
+}
+
+ParserResult Parser::_varHeaderTopic(Parser* p) {
+  // no checking for character [MQTT-3.3.2-1] [MQTT-3.3.2-2]
+  p->_packet.variableHeader.topic[p->_bytePos] = static_cast<char>(p->_data[p->_bytesRead]);
+  p->_bytePos++;
+  if (p->_bytePos == p->_packet.variableHeader.topicLength || p->_bytePos == EMC_MAX_TOPIC_LENGTH) {
+    p->_packet.variableHeader.topic[p->_bytePos] = 0x00;  // add c-string delimiter
+    emc_log_i("Packet variable header topic complete");
+    if (p->_packet.fixedHeader.packetType & (HeaderFlag.PUBLISH_QOS1 | HeaderFlag.PUBLISH_QOS2)) {
+      p->_parse = _varHeaderPacketId1;
+    } else if (p->_packet.payload.total == 0) {
+      p->_parse = _fixedHeader;
+      return ParserResult::packet;
+    } else {
+      p->_parse = _payloadPublish;
+    }
+  }
+  return ParserResult::awaitData;
+}
+
+ParserResult Parser::_payloadSuback(Parser* p) {
+  uint8_t data = p->_data[p->_bytesRead];
+  if (data < 0x03 || data == 0x80) {
+    p->_payloadBuffer[p->_bytePos] = data;
+    p->_bytePos++;
+  } else {
+    p->_parse = _fixedHeader;
+    emc_log_w("Invalid suback return code");
+    return ParserResult::protocolError;
+  }
+  if (p->_bytePos == p->_packet.payload.total) {
+    p->_parse = _fixedHeader;
+    emc_log_i("Packet complete");
+    return ParserResult::packet;
+  }
+  return ParserResult::awaitData;
+}
+
+ParserResult Parser::_payloadPublish(Parser* p) {
+  p->_packet.payload.index += p->_packet.payload.length;
+  p->_packet.payload.data = &p->_data[p->_bytesRead];
+  emc_log_i("payload: index %zu, total %zu, avail %zu/%zu", p->_packet.payload.index, p->_packet.payload.total, p->_len - p->_bytesRead, p->_len);
+  p->_packet.payload.length = std::min(p->_len - p->_bytesRead, p->_packet.payload.total - p->_packet.payload.index);
+  p->_bytesRead += p->_packet.payload.length - 1;  // compensate for increment in _parse-loop
+  if (p->_packet.payload.index + p->_packet.payload.length == p->_packet.payload.total) {
+    p->_parse = _fixedHeader;
+  }
+  return ParserResult::packet;
+}
+
+}  // end namespace espMqttClientInternals

lib/espMqttClient/src/Packets/Parser.h

@@ -0,0 +1,100 @@
+/*
+Copyright (c) 2022 Bert Melis. All rights reserved.
+
+This work is licensed under the terms of the MIT license.  
+For a copy, see <https://opensource.org/licenses/MIT> or
+the LICENSE file.
+*/
+
+#pragma once
+
+#include <stdint.h>
+#include <stddef.h>
+#include <algorithm>
+
+#include "../Config.h"
+#include "Constants.h"
+#include "../Logging.h"
+#include "RemainingLength.h"
+
+namespace espMqttClientInternals {
+
+struct IncomingPacket {
+  struct __attribute__((__packed__)) {
+    MQTTPacketType packetType;
+    union {
+      size_t remainingLength;
+      uint8_t remainingLengthRaw[4];
+    } remainingLength;
+  } fixedHeader;
+  struct __attribute__((__packed__)) {
+    uint16_t topicLength;
+    char topic[EMC_MAX_TOPIC_LENGTH + 1];  // + 1 for c-string delimiter
+    union {
+      struct {
+        uint8_t sessionPresent;
+        uint8_t returnCode;
+      } connackVarHeader;
+      uint16_t packetId;
+    } fixed;
+  } variableHeader;
+  struct {
+    const uint8_t* data;
+    size_t length;
+    size_t index;
+    size_t total;
+  } payload;
+
+  uint8_t qos() const;
+  bool retain() const;
+  bool dup() const;
+  void reset();
+};
+
+enum class ParserResult : uint8_t {
+  awaitData,
+  packet,
+  protocolError
+};
+
+class Parser;
+typedef ParserResult(*ParserFunc)(Parser*);
+
+class Parser {
+ public:
+  Parser();
+  ParserResult parse(const uint8_t* data, size_t len, size_t* bytesRead);
+  const IncomingPacket& getPacket() const;
+  void reset();
+
+ private:
+  // keep data variables in class to avoid copying on every iteration of the parser
+  const uint8_t* _data;
+  size_t _len;
+  size_t _bytesRead;
+  size_t _bytePos;
+  ParserFunc _parse;
+  IncomingPacket _packet;
+  uint8_t _payloadBuffer[EMC_PAYLOAD_BUFFER_SIZE];
+
+  static ParserResult _fixedHeader(Parser* p);
+  static ParserResult _remainingLengthFixed(Parser* p);
+  static ParserResult _remainingLengthNone(Parser* p);
+  static ParserResult _remainingLengthVariable(Parser* p);
+
+
+  static ParserResult _varHeaderConnack1(Parser* p);
+  static ParserResult _varHeaderConnack2(Parser* p);
+
+  static ParserResult _varHeaderPacketId1(Parser* p);
+  static ParserResult _varHeaderPacketId2(Parser* p);
+
+  static ParserResult _varHeaderTopicLength1(Parser* p);
+  static ParserResult _varHeaderTopicLength2(Parser* p);
+  static ParserResult _varHeaderTopic(Parser* p);
+
+  static ParserResult _payloadSuback(Parser* p);
+  static ParserResult _payloadPublish(Parser* p);
+};
+
+}  // end namespace espMqttClientInternals

lib/espMqttClient/src/Packets/RemainingLength.cpp

@@ -0,0 +1,57 @@
+/*
+Copyright (c) 2022 Bert Melis. All rights reserved.
+
+This work is licensed under the terms of the MIT license.  
+For a copy, see <https://opensource.org/licenses/MIT> or
+the LICENSE file.
+*/
+
+#include "RemainingLength.h"
+
+namespace espMqttClientInternals {
+
+int32_t decodeRemainingLength(const uint8_t* stream) {
+  uint32_t multiplier = 1;
+  int32_t remainingLength = 0;
+  uint8_t currentByte = 0;
+  uint8_t encodedByte;
+
+  do {
+    encodedByte = stream[currentByte++];
+    remainingLength += (encodedByte & 127) * multiplier;
+    if (multiplier > 128 * 128 * 128) {
+      emc_log_e("Malformed Remaining Length");
+      return -1;
+    }
+    multiplier *= 128;
+  } while ((encodedByte & 128) != 0);
+
+  return remainingLength;
+}
+
+uint8_t remainingLengthLength(uint32_t remainingLength) {
+  if (remainingLength < 128) return 1;
+  if (remainingLength < 16384) return 2;
+  if (remainingLength < 2097152) return 3;
+  if (remainingLength > 268435455) return 0;
+  return 4;
+}
+
+uint8_t encodeRemainingLength(uint32_t remainingLength, uint8_t* destination) {
+  uint8_t currentByte = 0;
+  uint8_t bytesNeeded = 0;
+
+  do {
+    uint8_t encodedByte = remainingLength % 128;
+    remainingLength /= 128;
+    if (remainingLength > 0) {
+      encodedByte = encodedByte | 128;
+    }
+    destination[currentByte++] = encodedByte;
+    bytesNeeded++;
+  } while (remainingLength > 0);
+
+  return bytesNeeded;
+}
+
+}  // namespace espMqttClientInternals

lib/espMqttClient/src/Packets/RemainingLength.h

@@ -0,0 +1,32 @@
+/*
+Copyright (c) 2022 Bert Melis. All rights reserved.
+
+This work is licensed under the terms of the MIT license.  
+For a copy, see <https://opensource.org/licenses/MIT> or
+the LICENSE file.
+*/
+
+#pragma once
+
+#include <stdint.h>
+
+#include "../Logging.h"
+
+namespace espMqttClientInternals {
+
+// Calculations are based on non normative comment in section 2.2.3 Remaining Length of the MQTT specification
+
+// returns decoded length based on input stream
+// stream is expected to contain full encoded remaining length
+// return -1 on error.
+int32_t decodeRemainingLength(const uint8_t* stream);
+
+
+// returns the number of bytes needed to encode the remaining length
+uint8_t remainingLengthLength(uint32_t remainingLength);
+
+// encodes the given remaining length to destination and returns number of bytes used
+// destination is expected to be large enough to hold the number of bytes needed
+uint8_t encodeRemainingLength(uint32_t remainingLength, uint8_t* destination);
+
+}  // namespace espMqttClientInternals

lib/espMqttClient/src/Packets/String.cpp

@@ -0,0 +1,26 @@
+/*
+Copyright (c) 2022 Bert Melis. All rights reserved.
+
+This work is licensed under the terms of the MIT license.  
+For a copy, see <https://opensource.org/licenses/MIT> or
+the LICENSE file.
+*/
+
+#include "String.h"
+
+namespace espMqttClientInternals {
+
+size_t encodeString(const char* source, uint8_t* dest) {
+  size_t length = strlen(source);
+  if (length > 65535) {
+    emc_log_e("String length error");
+    return 0;
+  }
+
+  dest[0] = static_cast<uint16_t>(length) >> 8;
+  dest[1] = static_cast<uint16_t>(length) & 0xFF;
+  memcpy(&dest[2], source, length);
+  return 2 + length;
+}
+
+}  // namespace espMqttClientInternals

lib/espMqttClient/src/Packets/String.h

@@ -0,0 +1,22 @@
+/*
+Copyright (c) 2022 Bert Melis. All rights reserved.
+
+This work is licensed under the terms of the MIT license.  
+For a copy, see <https://opensource.org/licenses/MIT> or
+the LICENSE file.
+*/
+
+#pragma once
+
+#include <stdint.h>
+#include <cstring>  // memcpy
+
+#include "../Logging.h"
+
+namespace espMqttClientInternals {
+
+// encodes the given source string into destination and returns number of bytes used
+// destination is expected to be large enough to hold the number of bytes needed
+size_t encodeString(const char* source, uint8_t* dest);
+
+}  // namespace espMqttClientInternals

lib/espMqttClient/src/Transport/ClientAsync.cpp

@@ -0,0 +1,58 @@
+/*
+Copyright (c) 2022 Bert Melis. All rights reserved.
+
+This work is licensed under the terms of the MIT license.  
+For a copy, see <https://opensource.org/licenses/MIT> or
+the LICENSE file.
+*/
+
+#if defined(ARDUINO_ARCH_ESP8266) || defined(ARDUINO_ARCH_ESP32)
+
+#include "ClientAsync.h"
+
+namespace espMqttClientInternals {
+
+ClientAsync::ClientAsync()
+: client()
+, availableData(0)
+, bufData(nullptr) {
+  // empty
+}
+
+bool ClientAsync::connect(IPAddress ip, uint16_t port) {
+  return client.connect(ip, port);
+}
+
+bool ClientAsync::connect(const char* host, uint16_t port) {
+  return client.connect(host, port);
+}
+
+size_t ClientAsync::write(const uint8_t* buf, size_t size) {
+  return client.write(reinterpret_cast<const char*>(buf), size);
+}
+
+int ClientAsync::read(uint8_t* buf, size_t size) {
+  size_t willRead = std::min(size, availableData);
+  memcpy(buf, bufData, std::min(size, availableData));
+  if (availableData > size) {
+    emc_log_w("Buffer is smaller than available data: %zu - %zu", size, availableData);
+  }
+  availableData = 0;
+  return willRead;
+}
+
+void ClientAsync::stop() {
+  client.close(false);
+}
+
+bool ClientAsync::connected() {
+  return client.connected();
+}
+
+bool ClientAsync::disconnected() {
+  return client.disconnected();
+}
+
+}  // namespace espMqttClientInternals
+
+#endif

lib/espMqttClient/src/Transport/ClientAsync.h

@@ -0,0 +1,44 @@
+/*
+Copyright (c) 2022 Bert Melis. All rights reserved.
+
+This work is licensed under the terms of the MIT license.  
+For a copy, see <https://opensource.org/licenses/MIT> or
+the LICENSE file.
+*/
+
+#if defined(ARDUINO_ARCH_ESP8266) || defined(ARDUINO_ARCH_ESP32)
+
+#pragma once
+
+#if defined(ARDUINO_ARCH_ESP32)
+  #include "freertos/FreeRTOS.h"
+  #include <AsyncTCP.h>
+#elif defined(ARDUINO_ARCH_ESP8266)
+  #include <ESPAsyncTCP.h>
+#endif
+
+#include "Transport.h"
+#include "../Config.h"
+#include "../Logging.h"
+
+namespace espMqttClientInternals {
+
+class ClientAsync : public Transport {
+ public:
+  ClientAsync();
+  bool connect(IPAddress ip, uint16_t port) override;
+  bool connect(const char* host, uint16_t port) override;
+  size_t write(const uint8_t* buf, size_t size) override;
+  int read(uint8_t* buf, size_t size) override;
+  void stop() override;
+  bool connected() override;
+  bool disconnected() override;
+
+  AsyncClient client;
+  size_t availableData;
+  uint8_t* bufData;
+};
+
+}  // namespace espMqttClientInternals
+
+#endif

lib/espMqttClient/src/Transport/ClientPosix.cpp

@@ -0,0 +1,92 @@
+/*
+Copyright (c) 2022 Bert Melis. All rights reserved.
+
+This work is licensed under the terms of the MIT license.  
+For a copy, see <https://opensource.org/licenses/MIT> or
+the LICENSE file.
+*/
+
+#include "ClientPosix.h"
+
+#if defined(__linux__)
+
+namespace espMqttClientInternals {
+
+ClientPosix::ClientPosix()
+: _sockfd(-1)
+, _host() {
+  // empty
+}
+
+ClientPosix::~ClientPosix() {
+  ClientPosix::stop();
+}
+
+bool ClientPosix::connect(IPAddress ip, uint16_t port) {
+  if (connected()) stop();
+
+  _sockfd = ::socket(AF_INET, SOCK_STREAM, 0);
+  if (_sockfd < 0) {
+    emc_log_e("Error %d opening socket", errno);
+  }
+
+  int flag = 1;
+  if (setsockopt(_sockfd, IPPROTO_TCP, TCP_NODELAY, &flag, sizeof(int)) < 0) {
+    emc_log_e("Error %d disabling nagle", errno);
+  }
+
+  memset(&_host, 0, sizeof(_host));
+  _host.sin_family = AF_INET;
+  _host.sin_addr.s_addr = htonl(uint32_t(ip));
+  _host.sin_port = ::htons(port);
+
+  int ret = ::connect(_sockfd, (struct sockaddr *)&_host, sizeof(_host));
+
+  if (ret < 0) {
+    emc_log_e("Error connecting: %d - (%d) %s", ret, errno, strerror(errno));
+    return false;
+  }
+
+  emc_log_i("Connected");
+  return true;
+}
+
+bool ClientPosix::connect(const char* host, uint16_t port) {
+  // tbi
+  (void) host;
+  (void) port;
+  return false;
+}
+
+size_t ClientPosix::write(const uint8_t* buf, size_t size) {
+  return ::send(_sockfd, buf, size, 0);
+}
+
+int ClientPosix::read(uint8_t* buf, size_t size) {
+  int ret = ::recv(_sockfd, buf, size, MSG_DONTWAIT);
+  /*
+  if (ret < 0) {
+    emc_log_e("Error reading: %s", strerror(errno));
+  }
+  */
+  return ret;
+}
+
+void ClientPosix::stop() {
+  if (_sockfd >= 0) {
+    ::close(_sockfd);
+    _sockfd = -1;
+  }
+}
+
+bool ClientPosix::connected() {
+  return _sockfd >= 0;
+}
+
+bool ClientPosix::disconnected() {
+  return _sockfd < 0;
+}
+
+}  // namespace espMqttClientInternals
+
+#endif

lib/espMqttClient/src/Transport/ClientPosix.h

@@ -0,0 +1,51 @@
+/*
+Copyright (c) 2022 Bert Melis. All rights reserved.
+
+This work is licensed under the terms of the MIT license.  
+For a copy, see <https://opensource.org/licenses/MIT> or
+the LICENSE file.
+*/
+
+#pragma once
+
+#if defined(__linux__)
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <string.h>
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <netinet/in.h>
+#include <netinet/tcp.h>
+#include <netdb.h>
+
+#include "Transport.h"  // includes IPAddress
+#include "../Logging.h"
+
+#ifndef EMC_POSIX_PEEK_SIZE
+#define EMC_POSIX_PEEK_SIZE 1500
+#endif
+
+namespace espMqttClientInternals {
+
+class ClientPosix : public Transport {
+ public:
+  ClientPosix();
+  ~ClientPosix();
+  bool connect(IPAddress ip, uint16_t port) override;
+  bool connect(const char* host, uint16_t port) override;
+  size_t write(const uint8_t* buf, size_t size) override;
+  int read(uint8_t* buf, size_t size) override;
+  void stop() override;
+  bool connected() override;
+  bool disconnected() override;
+
+ protected:
+  int _sockfd;
+  struct sockaddr_in _host;
+};
+
+}  // namespace espMqttClientInternals
+
+#endif

lib/espMqttClient/src/Transport/ClientSecureSync.cpp

@@ -0,0 +1,71 @@
+/*
+Copyright (c) 2022 Bert Melis. All rights reserved.
+
+This work is licensed under the terms of the MIT license.  
+For a copy, see <https://opensource.org/licenses/MIT> or
+the LICENSE file.
+*/
+
+#if defined(ARDUINO_ARCH_ESP8266) || defined(ARDUINO_ARCH_ESP32)
+
+#include "ClientSecureSync.h"
+#include <lwip/sockets.h>  // socket options
+
+namespace espMqttClientInternals {
+
+ClientSecureSync::ClientSecureSync()
+: client() {
+  // empty
+}
+
+bool ClientSecureSync::connect(IPAddress ip, uint16_t port) {
+  bool ret = client.connect(ip, port);  // implicit conversion of return code int --> bool
+  if (ret) {
+    #if defined(ARDUINO_ARCH_ESP8266)
+    client.setNoDelay(true);
+    #elif defined(ARDUINO_ARCH_ESP32)
+    // Set TCP option directly to bypass lack of working setNoDelay for WiFiClientSecure
+    int val = true;
+    client.setSocketOption(IPPROTO_TCP, TCP_NODELAY, &val, sizeof(int));
+    #endif
+  }
+  return ret;
+}
+
+bool ClientSecureSync::connect(const char* host, uint16_t port) {
+  bool ret = client.connect(host, port);  // implicit conversion of return code int --> bool
+  if (ret) {
+    #if defined(ARDUINO_ARCH_ESP8266)
+    client.setNoDelay(true);
+    #elif defined(ARDUINO_ARCH_ESP32)
+    // Set TCP option directly to bypass lack of working setNoDelay for WiFiClientSecure
+    int val = true;
+    client.setSocketOption(IPPROTO_TCP, TCP_NODELAY, &val, sizeof(int));
+    #endif
+  }
+  return ret;
+}
+
+size_t ClientSecureSync::write(const uint8_t* buf, size_t size) {
+  return client.write(buf, size);
+}
+
+int ClientSecureSync::read(uint8_t* buf, size_t size) {
+  return client.read(buf, size);
+}
+
+void ClientSecureSync::stop() {
+  client.stop();
+}
+
+bool ClientSecureSync::connected() {
+  return client.connected();
+}
+
+bool ClientSecureSync::disconnected() {
+  return !client.connected();
+}
+
+}  // namespace espMqttClientInternals
+
+#endif

lib/espMqttClient/src/Transport/ClientSecureSync.h

@@ -0,0 +1,34 @@
+/*
+Copyright (c) 2022 Bert Melis. All rights reserved.
+
+This work is licensed under the terms of the MIT license.  
+For a copy, see <https://opensource.org/licenses/MIT> or
+the LICENSE file.
+*/
+
+#pragma once
+
+#if defined(ARDUINO_ARCH_ESP8266) || defined(ARDUINO_ARCH_ESP32)
+
+#include <WiFiClientSecure.h>  // includes IPAddress
+
+#include "Transport.h"
+
+namespace espMqttClientInternals {
+
+class ClientSecureSync : public Transport {
+ public:
+  ClientSecureSync();
+  bool connect(IPAddress ip, uint16_t port) override;
+  bool connect(const char* host, uint16_t port) override;
+  size_t write(const uint8_t* buf, size_t size) override;
+  int read(uint8_t* buf, size_t size) override;
+  void stop() override;
+  bool connected() override;
+  bool disconnected() override;
+  WiFiClientSecure client;
+};
+
+}  // namespace espMqttClientInternals
+
+#endif

lib/espMqttClient/src/Transport/ClientSync.cpp

@@ -0,0 +1,71 @@
+/*
+Copyright (c) 2022 Bert Melis. All rights reserved.
+
+This work is licensed under the terms of the MIT license.  
+For a copy, see <https://opensource.org/licenses/MIT> or
+the LICENSE file.
+*/
+
+#if defined(ARDUINO_ARCH_ESP8266) || defined(ARDUINO_ARCH_ESP32)
+
+#include "ClientSync.h"
+#include <lwip/sockets.h>  // socket options
+
+namespace espMqttClientInternals {
+
+ClientSync::ClientSync()
+: client() {
+  // empty
+}
+
+bool ClientSync::connect(IPAddress ip, uint16_t port) {
+  bool ret = client.connect(ip, port);  // implicit conversion of return code int --> bool
+  if (ret) {
+    #if defined(ARDUINO_ARCH_ESP8266)
+    client.setNoDelay(true);
+    #elif defined(ARDUINO_ARCH_ESP32)
+    // Set TCP option directly to bypass lack of working setNoDelay for WiFiClientSecure (for consistency also here)
+    int val = true;
+    client.setSocketOption(IPPROTO_TCP, TCP_NODELAY, &val, sizeof(int));
+    #endif
+  }
+  return ret;
+}
+
+bool ClientSync::connect(const char* host, uint16_t port) {
+  bool ret = client.connect(host, port);  // implicit conversion of return code int --> bool
+  if (ret) {
+    #if defined(ARDUINO_ARCH_ESP8266)
+    client.setNoDelay(true);
+    #elif defined(ARDUINO_ARCH_ESP32)
+    // Set TCP option directly to bypass lack of working setNoDelay for WiFiClientSecure (for consistency also here)
+    int val = true;
+    client.setSocketOption(IPPROTO_TCP, TCP_NODELAY, &val, sizeof(int));
+    #endif
+  }
+  return ret;
+}
+
+size_t ClientSync::write(const uint8_t* buf, size_t size) {
+  return client.write(buf, size);
+}
+
+int ClientSync::read(uint8_t* buf, size_t size) {
+  return client.read(buf, size);
+}
+
+void ClientSync::stop() {
+  client.stop();
+}
+
+bool ClientSync::connected() {
+  return client.connected();
+}
+
+bool ClientSync::disconnected() {
+  return !client.connected();
+}
+
+}  // namespace espMqttClientInternals
+
+#endif

lib/espMqttClient/src/Transport/ClientSync.h

@@ -0,0 +1,34 @@
+/*
+Copyright (c) 2022 Bert Melis. All rights reserved.
+
+This work is licensed under the terms of the MIT license.  
+For a copy, see <https://opensource.org/licenses/MIT> or
+the LICENSE file.
+*/
+
+#pragma once
+
+#if defined(ARDUINO_ARCH_ESP8266) || defined(ARDUINO_ARCH_ESP32)
+
+#include <WiFiClient.h>  // includes IPAddress
+
+#include "Transport.h"
+
+namespace espMqttClientInternals {
+
+class ClientSync : public Transport {
+ public:
+  ClientSync();
+  bool connect(IPAddress ip, uint16_t port) override;
+  bool connect(const char* host, uint16_t port) override;
+  size_t write(const uint8_t* buf, size_t size) override;
+  int read(uint8_t* buf, size_t size) override;
+  void stop() override;
+  bool connected() override;
+  bool disconnected() override;
+  WiFiClient client;
+};
+
+}  // namespace espMqttClientInternals
+
+#endif

lib/espMqttClient/src/Transport/IPAddress.cpp

@@ -0,0 +1,32 @@
+/*
+Copyright (c) 2022 Bert Melis. All rights reserved.
+
+This work is licensed under the terms of the MIT license.  
+For a copy, see <https://opensource.org/licenses/MIT> or
+the LICENSE file.
+*/
+
+#if defined(__linux__)
+
+#include "IPAddress.h"
+
+IPAddress::IPAddress()
+: _address(0) {
+  // empty
+}
+
+IPAddress::IPAddress(uint8_t p0, uint8_t p1, uint8_t p2, uint8_t p3)
+: _address(0) {
+  _address = (uint32_t)p0 << 24 | (uint32_t)p1 << 16 | (uint32_t)p2 << 8 | p3;
+}
+
+IPAddress::IPAddress(uint32_t address)
+: _address(address) {
+  // empty
+}
+
+IPAddress::operator uint32_t() {
+  return _address;
+}
+
+#endif

lib/espMqttClient/src/Transport/IPAddress.h

@@ -0,0 +1,28 @@
+/*
+Copyright (c) 2022 Bert Melis. All rights reserved.
+
+This work is licensed under the terms of the MIT license.  
+For a copy, see <https://opensource.org/licenses/MIT> or
+the LICENSE file.
+*/
+
+#pragma once
+
+#if defined(ARDUINO)
+  #include <IPAddress.h>
+#else
+
+#include <stdint.h>
+
+class IPAddress {
+ public:
+  IPAddress();
+  IPAddress(uint8_t p0, uint8_t p1, uint8_t p2, uint8_t p3);
+  explicit IPAddress(uint32_t address);
+  operator uint32_t();
+
+ protected:
+  uint32_t _address;
+};
+
+#endif

lib/espMqttClient/src/Transport/Transport.h

@@ -0,0 +1,28 @@
+/*
+Copyright (c) 2022 Bert Melis. All rights reserved.
+
+This work is licensed under the terms of the MIT license.  
+For a copy, see <https://opensource.org/licenses/MIT> or
+the LICENSE file.
+*/
+
+#pragma once
+
+#include <stddef.h>  // size_t
+
+#include "IPAddress.h"
+
+namespace espMqttClientInternals {
+
+class Transport {
+ public:
+  virtual bool connect(IPAddress ip, uint16_t port) = 0;
+  virtual bool connect(const char* host, uint16_t port) = 0;
+  virtual size_t write(const uint8_t* buf, size_t size) = 0;
+  virtual int read(uint8_t* buf, size_t size) = 0;
+  virtual void stop() = 0;
+  virtual bool connected() = 0;
+  virtual bool disconnected() = 0;
+};
+
+}  // namespace espMqttClientInternals

lib/espMqttClient/src/TypeDefs.cpp

@@ -0,0 +1,51 @@
+/*
+Copyright (c) 2022 Bert Melis. All rights reserved.
+
+Parts are based on the original work of Marvin Roger:
+https://github.com/marvinroger/async-mqtt-client
+
+This work is licensed under the terms of the MIT license.  
+For a copy, see <https://opensource.org/licenses/MIT> or
+the LICENSE file.
+*/
+
+#include "TypeDefs.h"
+
+namespace espMqttClientTypes {
+
+const char* disconnectReasonToString(DisconnectReason reason) {
+  switch (reason) {
+    case DisconnectReason::USER_OK:                            return "No error";
+    case DisconnectReason::MQTT_UNACCEPTABLE_PROTOCOL_VERSION: return "Unacceptable protocol version";
+    case DisconnectReason::MQTT_IDENTIFIER_REJECTED:           return "Identified rejected";
+    case DisconnectReason::MQTT_SERVER_UNAVAILABLE:            return "Server unavailable";
+    case DisconnectReason::MQTT_MALFORMED_CREDENTIALS:         return "Malformed credentials";
+    case DisconnectReason::MQTT_NOT_AUTHORIZED:                return "Not authorized";
+    case DisconnectReason::TLS_BAD_FINGERPRINT:                return "Bad fingerprint";
+    case DisconnectReason::TCP_DISCONNECTED:                   return "TCP disconnected";
+    default:                                                   return "";
+  }
+}
+
+const char* subscribeReturncodeToString(SubscribeReturncode returnCode) {
+  switch (returnCode) {
+    case SubscribeReturncode::QOS0: return "QoS 0";
+    case SubscribeReturncode::QOS1: return "QoS 1";
+    case SubscribeReturncode::QOS2: return "QoS 2";
+    case SubscribeReturncode::FAIL: return "Failed";
+    default:                        return "";
+  }
+}
+
+const char* errorToString(Error error) {
+  switch (error) {
+    case Error::SUCCESS:             return "Success";
+    case Error::OUT_OF_MEMORY:       return "Out of memory";
+    case Error::MAX_RETRIES:         return "Maximum retries exceeded";
+    case Error::MALFORMED_PARAMETER: return "Malformed parameters";
+    case Error::MISC_ERROR:          return "Misc error";
+    default:                         return "";
+  }
+}
+
+}  // end namespace espMqttClientTypes

lib/espMqttClient/src/TypeDefs.h

@@ -0,0 +1,73 @@
+/*
+Copyright (c) 2022 Bert Melis. All rights reserved.
+
+Parts are based on the original work of Marvin Roger:
+https://github.com/marvinroger/async-mqtt-client
+
+This work is licensed under the terms of the MIT license.  
+For a copy, see <https://opensource.org/licenses/MIT> or
+the LICENSE file.
+*/
+
+#pragma once
+
+#include <stdint.h>
+#include <stddef.h>
+#include <functional>
+
+namespace espMqttClientTypes {
+
+enum class DisconnectReason : uint8_t {
+  USER_OK = 0,
+  MQTT_UNACCEPTABLE_PROTOCOL_VERSION = 1,
+  MQTT_IDENTIFIER_REJECTED = 2,
+  MQTT_SERVER_UNAVAILABLE = 3,
+  MQTT_MALFORMED_CREDENTIALS = 4,
+  MQTT_NOT_AUTHORIZED = 5,
+  TLS_BAD_FINGERPRINT = 6,
+  TCP_DISCONNECTED = 7
+};
+
+const char* disconnectReasonToString(DisconnectReason reason);
+
+enum class SubscribeReturncode : uint8_t {
+  QOS0 = 0x00,
+  QOS1 = 0x01,
+  QOS2 = 0x02,
+  FAIL = 0X80
+};
+
+const char* subscribeReturncodeToString(SubscribeReturncode returnCode);
+
+enum class Error : uint8_t {
+  SUCCESS = 0,
+  OUT_OF_MEMORY = 1,
+  MAX_RETRIES = 2,
+  MALFORMED_PARAMETER = 3,
+  MISC_ERROR = 4
+};
+
+const char* errorToString(Error error);
+
+struct MessageProperties {
+  uint8_t qos;
+  bool dup;
+  bool retain;
+  uint16_t packetId;
+};
+
+typedef std::function<void(bool sessionPresent)> OnConnectCallback;
+typedef std::function<void(DisconnectReason reason)> OnDisconnectCallback;
+typedef std::function<void(uint16_t packetId, const SubscribeReturncode* returncodes, size_t len)> OnSubscribeCallback;
+typedef std::function<void(uint16_t packetId)> OnUnsubscribeCallback;
+typedef std::function<void(const MessageProperties& properties, const char* topic, const uint8_t* payload, size_t len, size_t index, size_t total)> OnMessageCallback;
+typedef std::function<void(uint16_t packetId)> OnPublishCallback;
+typedef std::function<size_t(uint8_t* data, size_t maxSize, size_t index)> PayloadCallback;
+typedef std::function<void(uint16_t packetId, Error error)> OnErrorCallback;
+
+enum class UseInternalTask {
+  NO = 0,
+  YES = 1,
+};
+
+}  // end namespace espMqttClientTypes

lib/espMqttClient/src/espMqttClient.cpp

@@ -0,0 +1,113 @@
+/*
+Copyright (c) 2022 Bert Melis. All rights reserved.
+
+This work is licensed under the terms of the MIT license.  
+For a copy, see <https://opensource.org/licenses/MIT> or
+the LICENSE file.
+*/
+
+#include "espMqttClient.h"
+
+#if defined(ARDUINO_ARCH_ESP8266)
+espMqttClient::espMqttClient()
+: MqttClientSetup(espMqttClientTypes::UseInternalTask::NO)
+, _client() {
+  _transport = &_client;
+}
+
+espMqttClientSecure::espMqttClientSecure()
+: MqttClientSetup(espMqttClientTypes::UseInternalTask::NO)
+, _client() {
+  _transport = &_client;
+}
+
+espMqttClientSecure& espMqttClientSecure::setInsecure() {
+  _client.client.setInsecure();
+  return *this;
+}
+
+espMqttClientSecure& espMqttClientSecure::setFingerprint(const uint8_t fingerprint[20]) {
+  _client.client.setFingerprint(fingerprint);
+  return *this;
+}
+
+espMqttClientSecure& espMqttClientSecure::setTrustAnchors(const X509List *ta) {
+  _client.client.setTrustAnchors(ta);
+  return *this;
+}
+
+espMqttClientSecure& espMqttClientSecure::setClientRSACert(const X509List *cert, const PrivateKey *sk) {
+  _client.client.setClientRSACert(cert, sk);
+  return *this;
+}
+
+espMqttClientSecure& espMqttClientSecure::setClientECCert(const X509List *cert, const PrivateKey *sk, unsigned allowed_usages, unsigned cert_issuer_key_type) {
+  _client.client.setClientECCert(cert, sk, allowed_usages, cert_issuer_key_type);
+  return *this;
+}
+
+espMqttClientSecure& espMqttClientSecure::setCertStore(CertStoreBase *certStore) {
+  _client.client.setCertStore(certStore);
+  return *this;
+}
+#endif
+
+#if defined(ARDUINO_ARCH_ESP32)
+espMqttClient::espMqttClient(espMqttClientTypes::UseInternalTask useInternalTask)
+: MqttClientSetup(useInternalTask)
+, _client() {
+  _transport = &_client;
+}
+
+espMqttClient::espMqttClient(uint8_t priority, uint8_t core)
+: MqttClientSetup(espMqttClientTypes::UseInternalTask::YES, priority, core)
+, _client() {
+  _transport = &_client;
+}
+
+espMqttClientSecure::espMqttClientSecure(espMqttClientTypes::UseInternalTask useInternalTask)
+: MqttClientSetup(useInternalTask)
+, _client() {
+  _transport = &_client;
+}
+
+espMqttClientSecure::espMqttClientSecure(uint8_t priority, uint8_t core)
+: MqttClientSetup(espMqttClientTypes::UseInternalTask::YES, priority, core)
+, _client() {
+  _transport = &_client;
+}
+
+espMqttClientSecure& espMqttClientSecure::setInsecure() {
+  _client.client.setInsecure();
+  return *this;
+}
+
+espMqttClientSecure& espMqttClientSecure::setCACert(const char* rootCA) {
+  _client.client.setCACert(rootCA);
+  return *this;
+}
+
+espMqttClientSecure& espMqttClientSecure::setCertificate(const char* clientCa) {
+  _client.client.setCertificate(clientCa);
+  return *this;
+}
+
+espMqttClientSecure& espMqttClientSecure::setPrivateKey(const char* privateKey) {
+  _client.client.setPrivateKey(privateKey);
+  return *this;
+}
+
+espMqttClientSecure& espMqttClientSecure::setPreSharedKey(const char* pskIdent, const char* psKey) {
+  _client.client.setPreSharedKey(pskIdent, psKey);
+  return *this;
+}
+
+#endif
+
+#if defined(__linux__)
+espMqttClient::espMqttClient()
+: MqttClientSetup(espMqttClientTypes::UseInternalTask::NO)
+, _client() {
+  _transport = &_client;
+}
+#endif

lib/espMqttClient/src/espMqttClient.h

@@ -0,0 +1,80 @@
+/*
+Copyright (c) 2022 Bert Melis. All rights reserved.
+
+API is based on the original work of Marvin Roger:
+https://github.com/marvinroger/async-mqtt-client
+
+This work is licensed under the terms of the MIT license.  
+For a copy, see <https://opensource.org/licenses/MIT> or
+the LICENSE file.
+*/
+
+#pragma once
+
+#if defined(ARDUINO_ARCH_ESP8266) || defined(ARDUINO_ARCH_ESP32)
+#include "Transport/ClientSync.h"
+#include "Transport/ClientSecureSync.h"
+#elif defined(__linux__)
+#include "Transport/ClientPosix.h"
+#endif
+
+#include "MqttClientSetup.h"
+
+#if defined(ARDUINO_ARCH_ESP8266)
+class espMqttClient : public MqttClientSetup<espMqttClient> {
+ public:
+  espMqttClient();
+
+ protected:
+  espMqttClientInternals::ClientSync _client;
+};
+
+class espMqttClientSecure : public MqttClientSetup<espMqttClientSecure> {
+ public:
+  espMqttClientSecure();
+  espMqttClientSecure& setInsecure();
+  espMqttClientSecure& setFingerprint(const uint8_t fingerprint[20]);
+  espMqttClientSecure& setTrustAnchors(const X509List *ta);
+  espMqttClientSecure& setClientRSACert(const X509List *cert, const PrivateKey *sk);
+  espMqttClientSecure& setClientECCert(const X509List *cert, const PrivateKey *sk, unsigned allowed_usages, unsigned cert_issuer_key_type);
+  espMqttClientSecure& setCertStore(CertStoreBase *certStore);
+
+ protected:
+  espMqttClientInternals::ClientSecureSync _client;
+};
+#endif
+
+#if defined(ARDUINO_ARCH_ESP32)
+class espMqttClient : public MqttClientSetup<espMqttClient> {
+ public:
+  explicit espMqttClient(espMqttClientTypes::UseInternalTask useInternalTask);
+  explicit espMqttClient(uint8_t priority = 1, uint8_t core = 1);
+
+ protected:
+  espMqttClientInternals::ClientSync _client;
+};
+
+class espMqttClientSecure : public MqttClientSetup<espMqttClientSecure> {
+ public:
+  explicit espMqttClientSecure(espMqttClientTypes::UseInternalTask useInternalTask);
+  explicit espMqttClientSecure(uint8_t priority = 1, uint8_t core = 1);
+  espMqttClientSecure& setInsecure();
+  espMqttClientSecure& setCACert(const char* rootCA);
+  espMqttClientSecure& setCertificate(const char* clientCa);
+  espMqttClientSecure& setPrivateKey(const char* privateKey);
+  espMqttClientSecure& setPreSharedKey(const char* pskIdent, const char* psKey);
+
+ protected:
+  espMqttClientInternals::ClientSecureSync _client;
+};
+#endif
+
+#if defined(__linux__)
+class espMqttClient : public MqttClientSetup<espMqttClient> {
+ public:
+  espMqttClient();
+
+ protected:
+  espMqttClientInternals::ClientPosix _client;
+};
+#endif

lib/espMqttClient/src/espMqttClientAsync.cpp

@@ -0,0 +1,61 @@
+/*
+Copyright (c) 2022 Bert Melis. All rights reserved.
+
+This work is licensed under the terms of the MIT license.  
+For a copy, see <https://opensource.org/licenses/MIT> or
+the LICENSE file.
+*/
+
+#if defined(ARDUINO_ARCH_ESP8266) || defined(ARDUINO_ARCH_ESP32)
+
+#include "espMqttClientAsync.h"
+
+espMqttClientAsync::espMqttClientAsync()
+: MqttClientSetup(espMqttClientTypes::UseInternalTask::NO)
+, _clientAsync() {
+  _transport = &_clientAsync;
+  _clientAsync.client.onConnect(onConnectCb, this);
+  _clientAsync.client.onDisconnect(onDisconnectCb, this);
+  _clientAsync.client.onData(onDataCb, this);
+  _clientAsync.client.onPoll(onPollCb, this);
+}
+
+bool espMqttClientAsync::connect() {
+  bool ret = MqttClient::connect();
+  loop();
+  return ret;
+}
+
+void espMqttClientAsync::_setupClient(espMqttClientAsync* c) {
+  (void)c;
+}
+
+void espMqttClientAsync::onConnectCb(void* a, AsyncClient* c) {
+  c->setNoDelay(true);
+  espMqttClientAsync* client = reinterpret_cast<espMqttClientAsync*>(a);
+  client->_state = MqttClient::State::connectingTcp2;
+  client->loop();
+}
+
+void espMqttClientAsync::onDataCb(void* a, AsyncClient* c, void* data, size_t len) {
+  (void)c;
+  espMqttClientAsync* client = reinterpret_cast<espMqttClientAsync*>(a);
+  client->_clientAsync.bufData = reinterpret_cast<uint8_t*>(data);
+  client->_clientAsync.availableData = len;
+  client->loop();
+}
+
+void espMqttClientAsync::onDisconnectCb(void* a, AsyncClient* c) {
+  (void)c;
+  espMqttClientAsync* client = reinterpret_cast<espMqttClientAsync*>(a);
+  client->_state = MqttClient::State::disconnectingTcp2;
+  client->loop();
+}
+
+void espMqttClientAsync::onPollCb(void* a, AsyncClient* c) {
+  (void)c;
+  espMqttClientAsync* client = reinterpret_cast<espMqttClientAsync*>(a);
+  client->loop();
+}
+
+#endif

lib/espMqttClient/src/espMqttClientAsync.h

@@ -0,0 +1,36 @@
+/*
+Copyright (c) 2022 Bert Melis. All rights reserved.
+
+API is based on the original work of Marvin Roger:
+https://github.com/marvinroger/async-mqtt-client
+
+This work is licensed under the terms of the MIT license.  
+For a copy, see <https://opensource.org/licenses/MIT> or
+the LICENSE file.
+*/
+
+#pragma once
+
+#if defined(ARDUINO_ARCH_ESP8266) || defined(ARDUINO_ARCH_ESP32)
+
+#include "Transport/ClientAsync.h"
+
+#include "MqttClientSetup.h"
+
+class espMqttClientAsync : public MqttClientSetup<espMqttClientAsync> {
+ public:
+  espMqttClientAsync();
+  bool connect();
+
+ protected:
+  espMqttClientInternals::ClientAsync _clientAsync;
+  static void _setupClient(espMqttClientAsync* c);
+  static void _disconnectClient(espMqttClientAsync* c);
+
+  static void onConnectCb(void* a, AsyncClient* c);
+  static void onDataCb(void* a, AsyncClient* c, void* data, size_t len);
+  static void onDisconnectCb(void* a, AsyncClient* c);
+  static void onPollCb(void* a, AsyncClient* c);
+};
+
+#endif

lib/framework/ESP8266React.h

@@ -59,7 +59,7 @@ class ESP8266React {
         return &_mqttSettingsService;
     }
 
-    AsyncMqttClient * getMqttClient() {
+    espMqttClient * getMqttClient() {
         return _mqttSettingsService.getMqttClient();
     }
 

lib/framework/MqttPubSub.h

@@ -1,163 +0,0 @@
-#ifndef MqttPubSub_h
-#define MqttPubSub_h
-
-#include <StatefulService.h>
-#include <AsyncMqttClient.h>
-
-using namespace std::placeholders; // for `_1` etc
-
-#define MQTT_ORIGIN_ID "mqtt"
-
-template <class T>
-class MqttConnector {
-  protected:
-    StatefulService<T> * _statefulService;
-    AsyncMqttClient *    _mqttClient;
-    size_t               _bufferSize;
-
-    MqttConnector(StatefulService<T> * statefulService, AsyncMqttClient * mqttClient, size_t bufferSize)
-        : _statefulService(statefulService)
-        , _mqttClient(mqttClient)
-        , _bufferSize(bufferSize) {
-        _mqttClient->onConnect(std::bind(&MqttConnector::onConnect, this));
-    }
-
-    virtual void onConnect() = 0;
-
-  public:
-    inline AsyncMqttClient * getMqttClient() const {
-        return _mqttClient;
-    }
-};
-
-template <class T>
-class MqttPub : virtual public MqttConnector<T> {
-  public:
-    MqttPub(JsonStateReader<T>   stateReader,
-            StatefulService<T> * statefulService,
-            AsyncMqttClient *    mqttClient,
-            const String &       pubTopic   = "",
-            size_t               bufferSize = DEFAULT_BUFFER_SIZE)
-        : MqttConnector<T>(statefulService, mqttClient, bufferSize)
-        , _stateReader(stateReader)
-        , _pubTopic(pubTopic) {
-        MqttConnector<T>::_statefulService->addUpdateHandler([&](const String & originId) { publish(); }, false);
-    }
-
-    void setPubTopic(const String & pubTopic) {
-        _pubTopic = pubTopic;
-        publish();
-    }
-
-  protected:
-    virtual void onConnect() {
-        publish();
-    }
-
-  private:
-    JsonStateReader<T> _stateReader;
-    String             _pubTopic;
-
-    void publish() {
-        if (_pubTopic.length() > 0 && MqttConnector<T>::_mqttClient->connected()) {
-            // serialize to json doc
-            DynamicJsonDocument json(MqttConnector<T>::_bufferSize);
-            JsonObject          jsonObject = json.to<JsonObject>();
-            MqttConnector<T>::_statefulService->read(jsonObject, _stateReader);
-
-            // serialize to string
-            String payload;
-            serializeJson(json, payload);
-
-            // publish the payload
-            MqttConnector<T>::_mqttClient->publish(_pubTopic.c_str(), 0, false, payload.c_str());
-        }
-    }
-};
-
-template <class T>
-class MqttSub : virtual public MqttConnector<T> {
-  public:
-    MqttSub(JsonStateUpdater<T>  stateUpdater,
-            StatefulService<T> * statefulService,
-            AsyncMqttClient *    mqttClient,
-            const String &       subTopic   = "",
-            size_t               bufferSize = DEFAULT_BUFFER_SIZE)
-        : MqttConnector<T>(statefulService, mqttClient, bufferSize)
-        , _stateUpdater(stateUpdater)
-        , _subTopic(subTopic) {
-        MqttConnector<T>::_mqttClient->onMessage(std::bind(&MqttSub::onMqttMessage, this, _1, _2, _3, _4, _5, _6));
-    }
-
-    void setSubTopic(const String & subTopic) {
-        if (!_subTopic.equals(subTopic)) {
-            // unsubscribe from the existing topic if one was set
-            if (_subTopic.length() > 0) {
-                MqttConnector<T>::_mqttClient->unsubscribe(_subTopic.c_str());
-            }
-            // set the new topic and re-configure the subscription
-            _subTopic = subTopic;
-            subscribe();
-        }
-    }
-
-  protected:
-    virtual void onConnect() {
-        subscribe();
-    }
-
-  private:
-    JsonStateUpdater<T> _stateUpdater;
-    String              _subTopic;
-
-    void subscribe() {
-        if (_subTopic.length() > 0) {
-            MqttConnector<T>::_mqttClient->subscribe(_subTopic.c_str(), 2);
-        }
-    }
-
-    void onMqttMessage(char * topic, char * payload, AsyncMqttClientMessageProperties properties, size_t len, size_t index, size_t total) {
-        // we only care about the topic we are watching in this class
-        if (strcmp(_subTopic.c_str(), topic)) {
-            return;
-        }
-
-        // deserialize from string
-        DynamicJsonDocument  json(MqttConnector<T>::_bufferSize);
-        DeserializationError error = deserializeJson(json, payload, len);
-        if (!error && json.is<JsonObject>()) {
-            JsonObject jsonObject = json.as<JsonObject>();
-            MqttConnector<T>::_statefulService->update(jsonObject, _stateUpdater, MQTT_ORIGIN_ID);
-        }
-    }
-};
-
-template <class T>
-class MqttPubSub : public MqttPub<T>, public MqttSub<T> {
-  public:
-    MqttPubSub(JsonStateReader<T>   stateReader,
-               JsonStateUpdater<T>  stateUpdater,
-               StatefulService<T> * statefulService,
-               AsyncMqttClient *    mqttClient,
-               const String &       pubTopic   = "",
-               const String &       subTopic   = "",
-               size_t               bufferSize = DEFAULT_BUFFER_SIZE)
-        : MqttConnector<T>(statefulService, mqttClient, bufferSize)
-        , MqttPub<T>(stateReader, statefulService, mqttClient, pubTopic, bufferSize)
-        , MqttSub<T>(stateUpdater, statefulService, mqttClient, subTopic, bufferSize) {
-    }
-
-  public:
-    void configureTopics(const String & pubTopic, const String & subTopic) {
-        MqttSub<T>::setSubTopic(subTopic);
-        MqttPub<T>::setPubTopic(pubTopic);
-    }
-
-  protected:
-    void onConnect() {
-        MqttSub<T>::onConnect();
-        MqttPub<T>::onConnect();
-    }
-};
-
-#endif

lib/framework/MqttSettingsService.cpp

@@ -33,8 +33,8 @@ MqttSettingsService::MqttSettingsService(AsyncWebServer * server, FS * fs, Secur
     , _retainedPassword(nullptr)
     , _reconfigureMqtt(false)
     , _disconnectedAt(0)
-    , _disconnectReason(AsyncMqttClientDisconnectReason::TCP_DISCONNECTED)
+    , _disconnectReason(espMqttClientTypes::DisconnectReason::TCP_DISCONNECTED)
-    , _mqttClient() {
+    , _mqttClient(espMqttClientTypes::UseInternalTask::NO) {
     WiFi.onEvent(std::bind(&MqttSettingsService::WiFiEvent, this, _1, _2));
     _mqttClient.onConnect(std::bind(&MqttSettingsService::onMqttConnect, this, _1));
     _mqttClient.onDisconnect(std::bind(&MqttSettingsService::onMqttDisconnect, this, _1));
@@ -51,12 +51,13 @@ void MqttSettingsService::begin() {
 void MqttSettingsService::loop() {
     if (_reconfigureMqtt || (_disconnectedAt && (uint32_t)(uuid::get_uptime() - _disconnectedAt) >= MQTT_RECONNECTION_DELAY)) {
         // reconfigure MQTT client
-        configureMqtt();
+        _disconnectedAt = uuid::get_uptime();
-
+        if (configureMqtt()) {
-        // clear the reconnection flags
-        _reconfigureMqtt = false;
             _disconnectedAt = 0;
         }
+        _reconfigureMqtt = false;
+    }
+    _mqttClient.loop();
 }
 
 bool MqttSettingsService::isEnabled() {
@@ -71,22 +72,27 @@ const char * MqttSettingsService::getClientId() {
     return _mqttClient.getClientId();
 }
 
-AsyncMqttClientDisconnectReason MqttSettingsService::getDisconnectReason() {
+espMqttClientTypes::DisconnectReason MqttSettingsService::getDisconnectReason() {
     return _disconnectReason;
 }
 
-AsyncMqttClient * MqttSettingsService::getMqttClient() {
+espMqttClient * MqttSettingsService::getMqttClient() {
     return &_mqttClient;
 }
 
 void MqttSettingsService::onMqttConnect(bool sessionPresent) {
+    // _disconnectedAt = 0;
+    emsesp::EMSESP::mqtt_.on_connect();
     // emsesp::EMSESP::logger().info("Connected to MQTT, %s", (sessionPresent) ? ("with persistent session") : ("without persistent session"));
 }
 
-void MqttSettingsService::onMqttDisconnect(AsyncMqttClientDisconnectReason reason) {
+void MqttSettingsService::onMqttDisconnect(espMqttClientTypes::DisconnectReason reason) {
     // emsesp::EMSESP::logger().info("Disconnected from MQTT reason: %d", (uint8_t)reason);
     _disconnectReason = reason;
+    if (!_disconnectedAt) {
         _disconnectedAt = uuid::get_uptime();
+    }
+    emsesp::EMSESP::mqtt_.on_disconnect(reason);
 }
 
 void MqttSettingsService::onConfigUpdated() {
@@ -121,7 +127,7 @@ void MqttSettingsService::WiFiEvent(WiFiEvent_t event, WiFiEventInfo_t info) {
     }
 }
 
-void MqttSettingsService::configureMqtt() {
+bool MqttSettingsService::configureMqtt() {
     // disconnect if connected
     _mqttClient.disconnect();
     // only connect if WiFi is connected and MQTT is enabled
@@ -137,11 +143,11 @@ void MqttSettingsService::configureMqtt() {
         _mqttClient.setClientId(retainCstr(_state.clientId.c_str(), &_retainedClientId));
         _mqttClient.setKeepAlive(_state.keepAlive);
         _mqttClient.setCleanSession(_state.cleanSession);
-        _mqttClient.setMaxTopicLength(FACTORY_MQTT_MAX_TOPIC_LENGTH); // hardcode. We don't take this from the settings anymore.
+        return _mqttClient.connect();
-        _mqttClient.connect();
         // } else {
         // emsesp::EMSESP::logger().info("Error configuring MQTT client");
     }
+    return false;
 }
 
 void MqttSettings::read(MqttSettings & settings, JsonObject & root) {

lib/framework/MqttSettingsService.h

@@ -4,7 +4,7 @@
 #include <StatefulService.h>
 #include <HttpEndpoint.h>
 #include <FSPersistence.h>
-#include <AsyncMqttClient.h>
+#include <espMqttClient.h>
 #include <ESPUtils.h>
 
 #include <uuid/common.h>
@@ -109,8 +109,8 @@ class MqttSettingsService : public StatefulService<MqttSettings> {
     bool                                 isEnabled();
     bool                                 isConnected();
     const char *                         getClientId();
-    AsyncMqttClientDisconnectReason getDisconnectReason();
+    espMqttClientTypes::DisconnectReason getDisconnectReason();
-    AsyncMqttClient *               getMqttClient();
+    espMqttClient *                      getMqttClient();
 
   protected:
     void onConfigUpdated();
@@ -120,7 +120,7 @@ class MqttSettingsService : public StatefulService<MqttSettings> {
     FSPersistence<MqttSettings> _fsPersistence;
 
     // Pointers to hold retained copies of the mqtt client connection strings.
-    // This is required as AsyncMqttClient holds references to the supplied connection strings.
+    // This is required as espMqttClient holds references to the supplied connection strings.
     char * _retainedHost;
     char * _retainedClientId;
     char * _retainedUsername;
@@ -131,15 +131,15 @@ class MqttSettingsService : public StatefulService<MqttSettings> {
     unsigned long _disconnectedAt;
 
     // connection status
-    AsyncMqttClientDisconnectReason _disconnectReason;
+    espMqttClientTypes::DisconnectReason _disconnectReason;
 
     // the MQTT client instance
-    AsyncMqttClient _mqttClient;
+    espMqttClient _mqttClient;
 
     void WiFiEvent(WiFiEvent_t event, WiFiEventInfo_t info);
     void onMqttConnect(bool sessionPresent);
-    void onMqttDisconnect(AsyncMqttClientDisconnectReason reason);
+    void onMqttDisconnect(espMqttClientTypes::DisconnectReason reason);
-    void configureMqtt();
+    bool configureMqtt();
 };
 
 #endif

src/emsdevice.cpp

@@ -1706,14 +1706,14 @@ void EMSdevice::mqtt_ha_entity_config_create() {
             Mqtt::publish_ha_sensor_config(dv, name(), brand_to_char(), false, create_device_config);
             dv.add_state(DeviceValueState::DV_HA_CONFIG_CREATED);
             create_device_config = false; // only create the main config once
-        }
-
 #ifndef EMSESP_STANDALONE
-        if (ESP.getFreeHeap() < (65 * 1024)) {
+            // always create minimum one config
+            if (ESP.getMaxAllocHeap() < (6 * 1024) || (!emsesp::EMSESP::system_.PSram() && ESP.getFreeHeap() < (65 * 1024))) {
                 break;
             }
 #endif
         }
+    }
 
     ha_config_done(!create_device_config);
 }

src/emsesp.cpp

@@ -1297,6 +1297,9 @@ void EMSESP::incoming_telegram(uint8_t * data, const uint8_t length) {
                 LOG_ERROR("Last Tx write rejected by host");
                 txservice_.send_poll(); // close the bus
             }
+        } else if (tx_state == Telegram::Operation::TX_READ && length == 1) {
+            EMSbus::tx_state(Telegram::Operation::TX_READ); // reset Tx wait state
+            return;
         } else if (tx_state == Telegram::Operation::TX_READ) {
             // got a telegram with data in it. See if the src/dest matches that from the last one we sent and continue to process it
             uint8_t src  = data[0];

src/mqtt.cpp

@@ -23,7 +23,7 @@
 
 namespace emsesp {
 
-AsyncMqttClient * Mqtt::mqttClient_;
+espMqttClient * Mqtt::mqttClient_;
 
 // static parameters we make global
 std::string Mqtt::mqtt_base_;
@@ -461,30 +461,6 @@ void Mqtt::start() {
     // add the 'publish' command ('call system publish' in console or via API)
     Command::add(EMSdevice::DeviceType::SYSTEM, F_(publish), System::command_publish, FL_(publish_cmd));
 
-    mqttClient_->onConnect([this](bool sessionPresent) { on_connect(); });
-
-    mqttClient_->onDisconnect([this](AsyncMqttClientDisconnectReason reason) {
-        // only show the error once, not every 2 seconds
-        if (!connecting_ && first_connect_attempted_) {
-            return;
-        }
-        first_connect_attempted_ = true;
-        connecting_              = false;
-        if (reason == AsyncMqttClientDisconnectReason::TCP_DISCONNECTED) {
-            LOG_WARNING("MQTT disconnected: TCP");
-        } else if (reason == AsyncMqttClientDisconnectReason::MQTT_IDENTIFIER_REJECTED) {
-            LOG_WARNING("MQTT disconnected: Identifier Rejected");
-        } else if (reason == AsyncMqttClientDisconnectReason::MQTT_SERVER_UNAVAILABLE) {
-            LOG_WARNING("MQTT disconnected: Server unavailable");
-        } else if (reason == AsyncMqttClientDisconnectReason::MQTT_MALFORMED_CREDENTIALS) {
-            LOG_WARNING("MQTT disconnected: Malformed credentials");
-        } else if (reason == AsyncMqttClientDisconnectReason::MQTT_NOT_AUTHORIZED) {
-            LOG_WARNING("MQTT disconnected: Not authorized");
-        } else {
-            LOG_WARNING("MQTT disconnected: code %d", reason);
-        }
-    });
-
     // create last will topic with the base prefixed. It has to be static because asyncmqttclient destroys the reference
     static char will_topic[MQTT_TOPIC_MAX_SIZE];
     if (!mqtt_base_.empty()) {
@@ -493,8 +469,9 @@ void Mqtt::start() {
 
     mqttClient_->setWill(will_topic, 1, true, "offline"); // with qos 1, retain true
 
-    mqttClient_->onMessage([this](const char * topic, const char * payload, AsyncMqttClientMessageProperties properties, size_t len, size_t index, size_t total) {
+    mqttClient_->onMessage(
-        on_message(topic, payload, len); // receiving mqtt
+        [this](const espMqttClientTypes::MessageProperties & properties, const char * topic, const uint8_t * payload, size_t len, size_t index, size_t total) {
+            on_message(topic, (const char *)payload, len); // receiving mqtt
         });
 
     mqttClient_->onPublish([this](uint16_t packetId) {
@@ -555,6 +532,30 @@ bool Mqtt::get_publish_onchange(uint8_t device_type) {
     }
     return false;
 }
+void Mqtt::on_disconnect(espMqttClientTypes::DisconnectReason reason) {
+    // only show the error once, not every 2 seconds
+    if (!connecting_) {
+        return;
+    }
+    connecting_ = false;
+    if (reason == espMqttClientTypes::DisconnectReason::TCP_DISCONNECTED) {
+        LOG_WARNING("MQTT disconnected: TCP");
+    } else if (reason == espMqttClientTypes::DisconnectReason::MQTT_UNACCEPTABLE_PROTOCOL_VERSION) {
+        LOG_WARNING("MQTT disconnected: Unacceptable protocol version");
+    } else if (reason == espMqttClientTypes::DisconnectReason::MQTT_IDENTIFIER_REJECTED) {
+        LOG_WARNING("MQTT disconnected: Identifier Rejected");
+    } else if (reason == espMqttClientTypes::DisconnectReason::MQTT_SERVER_UNAVAILABLE) {
+        LOG_WARNING("MQTT disconnected: Server unavailable");
+    } else if (reason == espMqttClientTypes::DisconnectReason::MQTT_MALFORMED_CREDENTIALS) {
+        LOG_WARNING("MQTT disconnected: Malformed credentials");
+    } else if (reason == espMqttClientTypes::DisconnectReason::MQTT_NOT_AUTHORIZED) {
+        LOG_WARNING("MQTT disconnected: Not authorized");
+    } else if (reason == espMqttClientTypes::DisconnectReason::TLS_BAD_FINGERPRINT) {
+        LOG_WARNING("MQTT disconnected: Server fingerprint invalid");
+    } else {
+        LOG_WARNING("MQTT disconnected: code %d", reason);
+    }
+}
 
 // MQTT onConnect - when an MQTT connect is established
 void Mqtt::on_connect() {
@@ -680,7 +681,7 @@ void Mqtt::queue_message(const uint8_t operation, const std::string & topic, con
 #ifndef EMSESP_STANDALONE
     // anything below 60MB available free heap is dangerously low, so we stop adding to prevent a crash
     // instead of doing a mqtt_messages_.pop_front()
-    if (mqtt_messages_.size() >= MAX_MQTT_MESSAGES || ESP.getFreeHeap() < (60 * 1024)) {
+    if (mqtt_messages_.size() >= MAX_MQTT_MESSAGES || (!emsesp::EMSESP::system_.PSram() && ESP.getFreeHeap() < (60 * 1024))) {
         LOG_WARNING("Queue overflow (queue count=%d, topic=%s)", mqtt_messages_.size(), topic.c_str());
         mqtt_publish_fails_++;
         return; // don't add to top of queue
@@ -857,7 +858,8 @@ void Mqtt::process_queue() {
 
     // else try and publish it
     // this is where the *real* publish happens
-    uint16_t packet_id = mqttClient_->publish(topic, mqtt_qos_, message->retain, message->payload.c_str(), message->payload.size(), false, mqtt_message.id_);
+    // uint16_t packet_id = mqttClient_->publish(topic, mqtt_qos_, message->retain, message->payload.c_str(), message->payload.size(), false, mqtt_message.id_);
+    uint16_t packet_id = mqttClient_->publish(topic, mqtt_qos_, message->retain, message->payload.c_str());
     lasttopic_         = topic;
     lastpayload_       = message->payload;
 

src/mqtt.h

@@ -19,7 +19,7 @@
 #ifndef EMSESP_MQTT_H_
 #define EMSESP_MQTT_H_
 
-#include <AsyncMqttClient.h>
+#include <espMqttClient.h>
 
 #include "helpers.h"
 #include "system.h"
@@ -76,6 +76,7 @@ class Mqtt {
     static constexpr uint8_t MQTT_TOPIC_MAX_SIZE = 128; // fixed, not a user setting anymore
 
     static void on_connect();
+    static void on_disconnect(espMqttClientTypes::DisconnectReason reason);
 
     static void subscribe(const uint8_t device_type, const std::string & topic, mqtt_sub_function_p cb);
     static void subscribe(const std::string & topic);
@@ -129,7 +130,7 @@ class Mqtt {
 #endif
     }
 
-    static AsyncMqttClient * client() {
+    static espMqttClient * client() {
         return mqttClient_;
     }
 
@@ -266,7 +267,7 @@ class Mqtt {
   private:
     static uuid::log::Logger logger_;
 
-    static AsyncMqttClient * mqttClient_;
+    static espMqttClient * mqttClient_;
     static uint32_t          mqtt_message_id_;
 
     static constexpr uint32_t MQTT_PUBLISH_WAIT      = 100; // delay in ms between sending publishes, to account for large payloads
@@ -306,8 +307,6 @@ class Mqtt {
     uint32_t last_publish_heartbeat_  = 0;
     uint32_t last_publish_queue_      = 0;
 
-    bool first_connect_attempted_ = false;
-
     static bool     connecting_;
     static bool     initialized_;
     static uint32_t mqtt_publish_fails_;