thingsboard/thingsboard-client-sdk

Client SDK to connect with ThingsBoard IoT Platform from various IoT devices (Arduino, Espressif, etc.)

This library provides access to the ThingsBoard platform over the MQTT or HTTP(S) protocols.

Examples

The SDK comes with a number of example sketches. See Files --> Examples --> ThingsBoard within the Arduino application. Please review the complete guide for ESP32 Pico Kit GPIO control and DHT22 sensor monitoring available here.

Supported Frameworks

ThingsBoardArduinoSDK does not directly depend on any specific MQTT Client or HTTP Client implementation, instead any implementation of the IMQTT_Client or IHTTP Client can be used. Because there are no further dependencies on Arduino, besides the client that communicates it allows us to use this library with Arduino, when using the Arduino_MQTT_Client or with Espressif IDF when using the Espressif_MQTT_Client.

Example usage for Espressif can be found in the examples/0014-espressif_esp32_send_data folder, all other code portions can be implemented the same way only initialization of the needed dependencies is slightly different. Meaning internal call to ThingsBoard works the same on both Espressif and Arduino.

This is also the case, because the only always used dependency that is remaining, is ArduinoJson, which despite its name does not require any Arduino component. Please Note: you must use v6.x.x of this library as v7.x.x is not yet supported. Please see this issue for details as to why.

Installation

This project can be built with either PlatformIO, ESP IDF Extension or Arduino IDE.

The project can be found in the PlatformIO Registry, ESP Component registry or the Arduino libraries.

A description on how to include the library in you project can be found below for each of the aforementioned possible methods of integrating the project.

PlatformIO

To add an external library, the most important portion is the lib_deps specification, simply add thingsboard/ThingsBoard. There are multiple ways to define the version that should be fetched, but the most basic is simply getting the last released version, with the aforementioned line, to learn more see Package Specifications.

lib_deps=
    thingsboard/ThingsBoard

ESP IDF Extension

To add an external library, what needs to be done differs between versions. If an ESP-IDF version after and including v3.2.0 is used then the project can simply be added over the Component Manager.

To do that we can simply call idf.py add-dependency <DEPENDENCY>, with the name of the dependency as an argument. Similar to PlatformIO there are a multiple way to define the version that should be fetched, but the method below is the most basic to simply get the last released version, to learn more see Using Component Manager with a Project.

idf.py add-dependency "thingsboard/ThingsBoard"

If an ESP-IDF version prior to v3.2.0 is used then the component has to be added as a git submodule. Meaning the repository has to first be a git project, if that is not the case already simply install git and call git init in the folder containing your project.

Similar to the other call there are a multiple way to define the version that should be fetched, but the method below is the most basic to simply get the last released version, to learn more see Git Submodule Help page.

git submodule add https://github.com/thingsboard/thingsboard-client-sdk.git components/ThingsBoard

Arduino IDE

To add an external library, we simply have to open Tools -> Manage Libraries and then search for ThingsBoard then press the install button for the wanted version. See how to install library on Arduino IDE for more detailed information and some troubleshooting if the aforementioned method does not work.

Dependencies

Following dependencies are installed automatically or must be installed, too:

Installed automatically:

• ArduinoJSON — needed for dealing with the JSON payload that is sent to and received by ThingsBoard. Please Note: you must use v6.x.x of this library as v7.x.x is not yet supported. Please see this issue for details as to why.
• MQTT PubSub Client — for interacting with MQTT, when using the Arduino_MQTT_Client instance as an argument to ThingsBoard. Only installed if this library is used over Arduino IDE or PlatformIO with the Arduino framework.
• Arduino Http Client — for interacting with HTTP/S when using the Arduino_HTTP_Client instance as an argument to ThingsBoardHttp. Only installed if this library is used over Arduino IDE or PlatformIO with the Arduino framework.

Needs to be installed manually:

• MbedTLS Library — needed to create hashes for the OTA update for non Espressif boards.
• Arduino Timer - needed to create non-blocking callback timers for non Espressif boards.
• WiFiEsp Client — needed when using a Arduino Uno with a ESP8266.
• StreamUtils — needed when sending arbitrary amount of payload even if the buffer size is too small to hold that complete payload is wanted, aforementioned feature is automatically enabled if the library is installed.

Supported ThingsBoard Features

Example implementations for all base features, mentioned above, can be found in the examples folder. See the README.md in each example folder, to see which boards are supported and which functionality the example shows.

Over MQTT:

All possible features are implemented over MQTT over a specific IAPI_Implementation instance:

• Telemetry data upload / ThingsBoardSized
• Device attribute publish / ThingsBoardSized
• Server-side RPC / Server_Side_RPC
• Client-side RPC / Client_Side_RPC
• Request attribute values / Attribute_Request_Callback
• Attribute update subscription / Shared_Attribute_Update
• Device provisioning / Provision
• Device claiming / ThingsBoardSized
• Firmware OTA update / OTA_Firmware_Update

Over HTTP(S):

The remaining features have to be implemented by hand with the sendGetRequest or sendPostRequest method. See the ThingsBoard Documentation on how these features could be implemented. This is not done directly in the library, because most features require constant polling, whether an event occurred or not, this would cause massive overhead if it is done for all possible features and therefore not recommended.

• Telemetry data upload
• Device attribute publish

Troubleshooting

This troubleshooting guide contains common issues that are well known and can occur if the library is used wrongly. Ensure to read this section before creating a new GitHub Issue.

Enabling internal debug messages

If the device is causing problems that are not already described in more detail below, it might be useful to enable internal debug messages, which will allow the library to print more information about sent and received messages as well as internal processes. This is disabled per default to decrease the amount of logs and memory for the log strings on the flash.

// If not set the value is 0 per default, meaning it will only print internal error messages,
// set to 1 to also print debugging messages which might help to discern the exact place where a method fails
#define THINGSBOARD_ENABLE_DEBUG 1
#include <ThingsBoard.h>

Not enough space for JSON serialization

The buffer size for the serialized JSON is fixed to 64 bytes. The SDK will not send data if the size of it is bigger than the configured internal buffer size. Respective logs in the "Serial Monitor" window will indicate the condition:

[TB] Send buffer size (64) to small for the given payloads size (83), increase with setBufferSize accordingly or install the StreamUtils library

If that's the case, the buffer size for serialization should be increased. To do so, setBufferSize() method can be used or the send_buffer_size passed to the constructor can be increased as illustrated below:

// Initialize underlying client, used to establish a connection
WiFiClient espClient;

// Initalize the Mqtt client instance
Arduino_MQTT_Client mqttClient(espClient);

// The SDK setup with 64 bytes for JSON payload and 8 fields for JSON object
// ThingsBoard tb(mqttClient);

// The SDK setup with 128 bytes for JSON payload and 32 fields for JSON object
ThingsBoardSized<32> tb(mqttClient, 128, 128);

void setup() {
  // Increase internal buffer size after inital creation.
  tb.setBufferSize(128, 128);
}

Alternatively, it is possible to enable the mentioned THINGSBOARD_ENABLE_STREAM_UTILS option, which sends messages that are bigger than the given buffer size with a method that skips the internal buffer, be aware tough this only works for sent messages. The internal buffer size still has to be big enough to receive the biggest possible message received by the client that is sent by the server.

For that the only thing that needs to be done is to install the required StreamUtils library, see the Dependencies section.

Dynamic ThingsBoard usage

All internal methods call attempt to utilize the stack as far as possible and completely minimize heap usage, that is the reason why there are places in the library where template arguments are required. If that memory being on the heap is not an issue, it is possible to remove the need to enter those template arguments altogether. Simply enable the THINGSBOARD_ENABLE_DYNAMIC option like shown below.

// If not set the value is 0 per default,
// set to 1 if the MaxResponse template argument should be automatically deduced instead
#define THINGSBOARD_ENABLE_DYNAMIC 1
#include <ThingsBoard.h>

Too much data fields must be serialized

The sendAttributes and sendTelemetry methods, use the StaticJsonDocument this requires the MaxKeyValuePairAmount template argument to be passed in the method template list. If more key-value pairs are sent than specified, the "Serial Monitor" window will get a respective log showing an error:

[TB] Unable to serialize key-value json
[TB] Attempt too enter to many JSON fields into StaticJsonDocument (5), increase (MaxKeyValuePairAmount) (3) accordingly

To fix the issue we simply have to increase the template argument for the method to the actually required amount.

Alternatively to remove the need for the MaxKeyValuePairAmounttemplate argument in the method template list and to ensure the size the method has is always enough to send messages, see the Dynamic ThingsBoard section section. This makes the library use the DynamicJsonDocument instead of the default StaticJsonDocument. Be aware though as this places the json structure onto the heap.

Additionally, the StaticJsonDocument is also used to deserialize the received payload for every kind of response received by the server, besides the OTA binary data. This means that if the MaxResponse template argument is smaller than the amount of received key-value pairs, the "Serial Monitor" window will get a respective log showing an error:

[TB] Attempt too enter to many JSON fields into StaticJsonDocument (12), increase (MaxResponse) (8) accordingly

To fix the issue we simply have to increase the template argument for the method to the actually required amount.

// Initialize underlying client, used to establish a connection
WiFiClient espClient;

// Initalize the Mqtt client instance
Arduino_MQTT_Client mqttClient(espClient);

// The SDK setup with 64 bytes for JSON payload and 8 fields for JSON object
// ThingsBoard tb(mqttClient);

// The SDK setup with 128 bytes for JSON payload and 32 fields for JSON object
ThingsBoardSized<32> tb(mqttClient, 128, 128);

Alternatively to remove the need for the MaxResponsetemplate argument in the constructor template list and to ensure the size the buffer should have is always enough to hold received messages, see the Dynamic ThingsBoard section section. This makes the library use the DynamicJsonDocument instead of the default StaticJsonDocument. Be aware though as this places the json structure onto the heap.

Too many subscriptions

The possible event subscription classes that are passed to internal methods, use arrays which reside on the stack those require the MaxSubscriptions template argument to be passed in the constructor template list. The default value is 1, if the method call attempts to subscribe more than that many events in total, the "Serial Monitor" window will get a respective log showing an error:

[TB] Too many shared attribute update subscriptions, increase MaxSubscriptions or unsubscribe

Important is that both server-side RPC and request attribute values are temporary, meaning once the request has been received it is deleted, and it is therefore possible to subscribe another event again. However, all other subscriptions like client-side RPC or attribute update subscription are permanent meaning once the event has been subscribed we can only unsubscribe all events to make more room.

Additionally, every aforementioned type of request has its own array meaning one type of event subscription (client-side RPC) does not affect the possible amount for another event subscription (attribute update subscription). Therefore, the only thing that needs to be done is to increase the size accordingly.

// Initialize underlying client, used to establish a connection
WiFiClient espClient;

// Initalize the Mqtt client instance
Arduino_MQTT_Client mqttClient(espClient);

// Initialize used apis with Shared_Attribute_Update API with 1 maximum Shared_Attribute_Update subscription at once
// Shared_Attribute_Update shared_attr;

// Initialize used apis with Shared_Attribute_Update API with 2 maximum Shared_Attribute_Update subscription at once
Shared_Attribute_Update<2U> shared_attr;
const std::array<IAPI_Implementation*, 1U> apis = {
    &shared_attr
};

// The SDK setup with 64 bytes for JSON payload and 8 fields for JSON object
// ThingsBoard tb(mqttClient, Default_Payload, Default_Payload, apis);

// The SDK setup with 128 bytes for JSON payload and 32 fields for JSON object
ThingsBoardSized<32> tb(mqttClient, 128, 128, apis);

Alternatively, to remove the need for the MaxSubscriptions template argument in the constructor template list, see the Dynamic ThingsBoard section section. This will replace the internal implementation with a growing vector instead, meaning all the subscribed callback data will reside on the heap instead.

Too many attributes

The possible attribute values that are passed to the Shared_Attribute_Callback or Attribute_Request_Callback, use arrays which reside on the stack those require the MaxAttributes template argument to be passed in the constructor template list. The default value is 1, if we attempt to subscribe or request more attributes than that, the "Serial Monitor" window will get a respective log showing a crash:

Assertion `m_size < Capacity' failed.

Therefore, the only thing that needs to be done is to increase the size accordingly.

// Initialize underlying client, used to establish a connection
WiFiClient espClient;

// Initalize the Mqtt client instance
Arduino_MQTT_Client mqttClient(espClient);

// Initialize used apis with Shared_Attribute_Update API, 1 maximum Shared_Attribute_Update subscription at once, 1 maximum attribute subscribed per individual subscription
// Shared_Attribute_Update shared_attr;

// Initialize used apis with Shared_Attribute_Update API, 2 maximum Shared_Attribute_Update subscription at once, 5 maximum attribute subscribed per individual subscription
Shared_Attribute_Update<2U, 5U> shared_attr;
const std::array<IAPI_Implementation*, 1U> apis = {
    &shared_attr
};

// The SDK setup with 64 bytes for JSON payload and 8 fields for JSON object
// ThingsBoard tb(mqttClient, Default_Payload, Default_Payload, apis);

// The SDK setup with 128 bytes for JSON payload and 32 fields for JSON object
ThingsBoardSized<32> tb(mqttClient, 128, 128, apis);

Alternatively, to remove the need for the MaxAttributes template argument in the constructor template list, see the Dynamic ThingsBoard section section. This will replace the internal implementation with a growing vector instead, meaning all the subscribed attribute data will reside on the heap instead.

Server-side RPC response overflowed

The possible response in subscribed RPC_Callback methods, use the StaticJsonDocument this requires the MaxRPC template argument to be passed in the constructor template list. The default value is 0, if we attempt to return more key-value pairs in the JSON than that, the "Serial Monitor" window will get a respective log showing an error:

[TB] Server-side RPC response overflowed, increase MaxRPC (0)

The default size is only 0, because if a callback only uses the JsonDocument::set() method, it does not require additional memory. This is only the case if we attempt to add key-value pairs to the JsonDocument. Therefore, the only thing that needs to be done is to increase the size accordingly.

// Initialize underlying client, used to establish a connection
WiFiClient espClient;

// Initalize the Mqtt client instance
Arduino_MQTT_Client mqttClient(espClient);

// Initialize used apis with Shared_Attribute_Update API, 1 maximum Shared_Attribute_Update subscription at once, 0 maximum attribute serialized in the response
// Shared_Attribute_Update shared_attr;

// Initialize used apis with Server_Side_RPC API, 2 maximum Server_Side_RPC subscription at once, 1 maximum attribute serialized in the response
Server_Side_RPC<2U, 1U> rpc;
const std::array<IAPI_Implementation*, 1U> apis = {
    &rpc
};

// The SDK setup with 64 bytes for JSON payload and 8 fields for JSON object
// ThingsBoard tb(mqttClient, Default_Payload, Default_Payload, apis);

// The SDK setup with 128 bytes for JSON payload and 32 fields for JSON object
ThingsBoardSized<32> tb(mqttClient, 128, 128, apis);

Alternatively, to remove the need for the MaxRPC template argument in the constructor template list, see the Dynamic ThingsBoard section section. This will instead expect an additional parameter response size in the RPC_Callback constructor argument list, which shows the internal size the JsonDocument needs to have to contain the response. Use JSON_OBJECT_SIZE() and pass the amount of key value pair to calculate the estimated size. See https://arduinojson.org/v6/assistant/ for more information.

Server-side RPC response overflowed

The possible request in subscribed RPC_Request_Callback methods, use the StaticJsonDocument this requires the MaxRequestRPC template argument to be passed in the constructor template list. The default value is 1, if we attempt to send more key-value pairs in the JSON than that, the "Serial Monitor" window will get a respective log showing an error:

[TB] Client-side RPC request overflowed, increase MaxRequestRPC (2)

// Initialize underlying client, used to establish a connection
WiFiClient espClient;

// Initalize the Mqtt client instance
Arduino_MQTT_Client mqttClient(espClient);

// Initialize used apis with Shared_Attribute_Update API, 1 maximum Shared_Attribute_Update subscription at once, 1 maximum attribute serialized in the request
// Shared_Attribute_Update shared_attr;

// Initialize used apis with Server_Side_RPC API, 2 maximum Server_Side_RPC subscription at once, 2 maximum attribute serialized in the request
Client_Side_RPC<2U, 2U> request_rpc;
const std::array<IAPI_Implementation*, 1U> apis = {
    &request_rpc
};

// The SDK setup with 64 bytes for JSON payload and 8 fields for JSON object
// ThingsBoard tb(mqttClient, Default_Payload, Default_Payload, apis);

// The SDK setup with 128 bytes for JSON payload and 32 fields for JSON object
ThingsBoardSized<32> tb(mqttClient, 128, 128, apis);

Alternatively, to remove the need for the MaxRequestRPC template argument in the constructor template list, see the Dynamic ThingsBoard section section. This makes the library use the DynamicJsonDocument instead of the default StaticJsonDocument. Be aware though as this copies the requests onto the heap.

Tips and Tricks

Custom API Implementation Instance

The ThingsBoardSized class instance only supports a minimal subset of the actual API, see the Supported ThingsBoard Features section. But with the usage of the IAPI_Implementation base class, it is possible to write an own implementation that implements an additional API implementation or changes the behavior for an already existing API implementation.

For that a class needs to inherit the API_Implemenatation class and override the needed methods shown below:

#ifndef Custom_API_Implementation_h
#define Custom_API_Implementation_h

// Local includes.
#include "IAPI_Implementation.h"


class Custom_API_Implementation : public IAPI_Implementation {
  public:
    API_Process_Type Get_Process_Type() override {
        return API_Process_Type::JSON;
    }

    void Process_Response(char const * topic, uint8_t * payload, unsigned int length) override {
        // Nothing to do
    }

    void Process_Json_Response(char const * topic, JsonDocument const & data) override {
        // Nothing to do
    }

    bool Compare_Response_Topic(char const * topic) const override {
        return true;
    }

    bool Unsubscribe() override {
        return true;
    }

    bool Resubscribe_Topic() override {
        return true;
    }

#if !THINGSBOARD_USE_ESP_TIMER
    void loop() override {
        // Nothing to do
    }
#endif // !THINGSBOARD_USE_ESP_TIMER

    void Initialize() override {
        // Nothing to do
    }

    void Set_Client_Callbacks(Callback<void, IAPI_Implementation &>::function subscribe_api_callback, Callback<bool, char const * const, JsonDocument const &, size_t const &>::function send_json_callback, Callback<bool, char const * const, char const * const>::function send_json_string_callback, Callback<bool, char const * const>::function subscribe_topic_callback, Callback<bool, char const * const>::function unsubscribe_topic_callback, Callback<uint16_t>::function get_receive_size_callback, Callback<uint16_t>::function get_send_size_callback, Callback<bool, uint16_t, uint16_t>::function set_buffer_size_callback, Callback<size_t *>::function get_request_id_callback) override {
        // Nothing to do
    }
};

#endif // Custom_API_Implementation_h

Once that has been done it can simply be passed to the ThingsBoard instance, either using the constructor or using the Subscribe_IAPI_Implementation method.

// Initialize underlying client, used to establish a connection
WiFiClient espClient;

// Initalize the Mqtt client instance
Arduino_MQTT_Client mqttClient(espClient);

// Initialize used apis with Custom API
Custom_IAPI_Implementation custom_api;
const std::array<IAPI_Implementation*, 1U> apis = {
    &custom_api
};

// The SDK setup with 64 bytes for JSON payload, 8 fields for JSON object and maximal 7 API endpoints subscribed at once
// ThingsBoard tb(mqttClient, Default_Payload, Default_Payload, apis);

// The SDK setup with 128 bytes for JSON payload and 8 fields for JSON object and maximal 10 API endpoints subscribed at once
ThingsBoardSized<8, 10> tb(mqttClient, 128, 128, apis);

// Optional alternative way to subscribe the Custom API ater the class instance has already been created
// tb.Subscribe_IAPI_Implementation(custom_api);

Custom Updater Instance

When using the ThingsBoard class instance, the class used to flash the binary data onto the device is not hard coded, but instead the OTA_Update_Callback class expects an argument, the IUpdater implementation.

Thanks to it being an interface it allows an arbitrary implementation, meaning as long as the device can flash binary data and supports the C++ STL it supports OTA updates, with the ThingsBoard library.

Currently, implemented in the library itself are the Arduino_ESP32_Updater, which is used for flashing the binary data when using a ESP32 and Arduino, the Arduino_ESP8266_Updater which is used with the ESP8266 and Arduino, the Espressif_Updater which is used with the ESP32 and the Espressif IDF tool chain and lastly the SDCard_Updater which is used for both Arduino and the Espressif IDF to flash binary data onto an already initialized SD card.

If another device or feature wants to be supported, a custom interface implementation needs to be created. For that a class needs to inherit the IUpdater interface and override the needed methods shown below:

#include <IUpdater.h>

class Custom_Updater : public IUpdater {
  public:
    bool begin(size_t const & firmware_size) override {
        return true;
    }
  
    size_t write(uint8_t * payload, size_t const & total_bytes) override {
        return total_bytes;
    }
  
    void reset() override {
        // Nothing to do
    }
  
    bool end() override {
        return true;
    }
};

Once that has been done it can simply be passed instead of the Espressif_Updater, Arduino_ESP8266_Updater, Arduino_ESP32_Updater or SDCard_Updater instance.

// Initalize the Updater client instance used to flash binary to flash memory
Custom_Updater updater;

const OTA_Update_Callback callback(CURRENT_FIRMWARE_TITLE, CURRENT_FIRMWARE_VERSION, &updater, &finished_callback, &progress_callback, &update_starting_callback, FIRMWARE_FAILURE_RETRIES, FIRMWARE_PACKET_SIZE);

Custom HTTP Instance

When using the ThingsBoardHttp class instance, the protocol used to send the data to the HTTP broker is not hard coded, but instead the ThingsBoardHttp class expects the argument to a IHTTP_Client implementation.

Thanks to it being an interface it allows an arbitrary implementation, meaning the underlying HTTP client can be whatever the user decides, so it can for example be used to support platforms using Arduino or even Espressif IDF.

Currently, implemented in the library itself is the Arduino_HTTP_Client, which is simply a wrapper around the ArduinoHttpClient, see dependencies for whether the board you are using is supported or not.

If another device or feature wants to be supported, a custom interface implementation needs to be created. For that a class needs to inherit the IHTTP_Client interface and override the needed methods shown below:

#include <IHTTP_Client.h>

class Custom_HTTP_Client : public IHTTP_Client {
  public:
    void set_keep_alive(bool keep_alive) override {
        // Nothing to do
    }

    int connect(char const * host, uint16_t port) override {
        return 0;
    }

    void stop() override {
        // Nothing to do
    }

    int post(char const * url_path, char const * content_type, char const * request_body) override {
        return 0;
    }

    int get_response_status_code() override {
        return 200;
    }

    int get(char const * url_path) override {
        return 0;
    }

#if THINGSBOARD_ENABLE_STL
    std::string get_response_body() override {
        return std::string();
    }
#else
    String get_response_body() override {
        return String();
    }

#endif // THINGSBOARD_ENABLE_STL
};

Once that has been done it can simply be passed instead of the Arduino_HTTP_Client instance.

// Initialize underlying client, used to establish a connection
WiFiClient espClient;

// Initalize the Http client instance
Custom_HTTP_Client httpClient(espClient, THINGSBOARD_SERVER, THINGSBOARD_PORT);

// The SDK setup with 8 fields for JSON object
ThingsBoardHttp tb(httpClient, TOKEN, THINGSBOARD_SERVER, THINGSBOARD_PORT);

Custom MQTT Instance

When using the ThingsBoard class instance, the protocol used to send the data to the MQTT broker is not hard coded, but instead the ThingsBoard class expects the argument to a IMQTT_Client implementation.

Thanks to it being an interface it allows an arbitrary implementation, meaning the underlying MQTT client can be whatever the user decides, so it can for example be used to support platforms using Arduino or even Espressif IDF.

Currently, implemented in the library itself is the Arduino_MQTT_Client, which is simply a wrapper around the PubSubClient, see compatible Hardware for whether the board you are using is supported or not, useful when using Arduino. As well as the Espressif_MQTT_Client, which is a simple wrapper around the esp-mqtt, useful when using Espressif IDF with a ESP32.

If another device or feature wants to be supported, a custom interface implementation needs to be created. For that a class needs to inherit the IMQTT_Client interface and override the needed methods shown below:

#include <IMQTT_Client.h>

class Custom_MQTT_Client : public IMQTT_Client {
  public:
    void set_data_callback(Callback<void, char *, uint8_t *, unsigned int>::function callback) override {
        // Nothing to do
    }

    void set_connect_callback(Callback<void>::function callback) override {
        // Nothing to do
    }

    bool set_buffer_size(uint16_t buffer_size) override {
        return true;
    }

    uint16_t get_buffer_size() override {
        return 0U;
    }

    void set_server(char const * domain, uint16_t port) override {
        // Nothing to do
    }

    bool connect(char const * client_id, char const * user_name, char const * password) override {
        return true;
    }

    void disconnect() override {
        // Nothing to do
    }

    bool loop() override {
        return true;
    }

    bool publish(char const * topic, uint8_t const * payload, size_t const & length) override {
        return true;
    }

    bool subscribe(char const * topic) override {
        return true;
    }

    bool unsubscribe(char const * topic) override {
        return true;
    }

    bool connected() override {
        return true;
    }

#if THINGSBOARD_ENABLE_STREAM_UTILS

    bool begin_publish(char const * topic, size_t const & length) override {
        return true;
    }

    bool end_publish() override {
        return true;
    }

    //----------------------------------------------------------------------------
    // Print interface
    //----------------------------------------------------------------------------

    size_t write(uint8_t payload_byte) override {
        return 1U;
    }

    size_t write(uint8_t const * buffer, size_t const & size) override {
        return size;
    }

#endif // THINGSBOARD_ENABLE_STREAM_UTILS
};

Once that has been done it can simply be passed instead of the Arduino_MQTT_Client or the Espressif_MQTT_Client instance.

// Initialize underlying client, used to establish a connection
WiFiClient espClient;

// Initalize the Mqtt client instance
Custom_MQTT_Client mqttClient(espClient);

// The SDK setup with 64 bytes for JSON payload and 8 fields for JSON object
// ThingsBoard tb(mqttClient);

// The SDK setup with 128 bytes for JSON payload and 32 fields for JSON object
ThingsBoardSized<32> tb(mqttClient, 128, 128);

Custom Logger Instance

When using the ThingsBoard class instance, the class used to print internal warning messages is not hard coded, but instead the ThingsBoard class expects the template argument to a Logger implementation. See the Enabling internal debug messages section if the logger should also receive debug messages.

Thanks to it being a template parameter it allows an arbitrary implementation, meaning the underlying Logger client can be whatever the user decides, so it can for example be used to print the messages onto a serial card instead of the serial console.

Currently, implemented in the library itself is the DefaultLogger, which is simply a wrapper around a printf call. If the functionality wants to be extended, a custom implementation needs to be created. For that a class needs to fulfill the contract and implement the needed methods shown below:

class CustomLogger {
  public:
    template<typename ...Args>
    static int printfln(char const * format, Args const &... args) {
        return 0;
    }
};

Once that has been done it can simply be passed as the last template parameter.

// Initialize underlying client, used to establish a connection
WiFiClient espClient;

// Initalize the Mqtt client instance
Arduino_MQTT_Client mqttClient(espClient);

// The SDK setup with 64 bytes for JSON payload and 8 fields for JSON object
// ThingsBoard tb(mqttClient);

// The SDK setup with 128 bytes for JSON payload and 32 fields for JSON object
ThingsBoardSized<32, Default_Response_Amount, CustomLogger> tb(mqttClient, 128, 128);

Have a question or proposal?

You are welcome in our issues and Q&A forum.

License

This code is released under the MIT License.