MQTT client for embedded systems

The purpose of this project was to implement MQTT client library from scratch - keeping in mind requirements for usage in embedded systems. The most important features:

• written to be compliant with MQTT 3.1.1 - handles QoS 0, 1 and 2
• uses raw API of LwIP network stack - operating system is not required
• configurable maximum length of messages and maximum number of active conversations with the broker.

Examples on how to use the library

In the file main.c there is an example on how to use the library. It includes:

• initialization of the client, setting connection parameters and pointer to function returning elapsed time [ms] from start of the system
• setting functions to be called when message is sent/received or subscription is completed
• connection to the broker
• publishing messages and subscribing to topics
• looping to receive messages and handle keepalive.

Test setup

The library was run on NUCLEO-F429ZI development board, connection tested with Mosquitto broker.