coreMQTT Agent Library

The coreMQTT Agent library is a high level API that adds thread safety to the coreMQTT library. The library provides thread safe equivalents to the coreMQTT's APIs, greatly simplifying its use in multi-threaded environments. The coreMQTT Agent library manages the MQTT connection by serializing the access to the coreMQTT library and reducing implementation overhead (e.g., removing the need for the application to repeatedly call to MQTT_ProcessLoop). This allows your multi-threaded applications to share the same MQTT connection, and enables you to design an embedded application without having to worry about coreMQTT thread safety.

This library has gone through code quality checks including verification that no function has a GNU Complexity score over 8, and checks against deviations from mandatory rules in the MISRA coding standard. Deviations from the MISRA C:2012 guidelines are documented under MISRA Deviations. This library has also undergone both static code analysis from Coverity static analysis, and validation of memory safety through the CBMC automated reasoning tool.

See memory requirements for this library here.

Cloning this repository

This repo uses Git Submodules to bring in dependent components.

To clone using HTTPS:

git clone https://github.com/FreeRTOS/coreMQTT-Agent.git --recurse-submodules

Using SSH:

git clone [email protected]:FreeRTOS/coreMQTT-Agent.git --recurse-submodules

If you have downloaded the repo without using the --recurse-submodules argument, you need to run:

git submodule update --init --recursive

coreMQTT Agent Library Configurations

The MQTT Agent library uses the same core_mqtt_config.h configuration file as coreMQTT, with the addition of configuration constants listed at the top of core_mqtt_agent.h and core_mqtt_agent_command_functions.h. Documentation for these configurations can be found here.

To provide values for these configuration values, they must be either:

• Defined in core_mqtt_config.h used by coreMQTT OR
• Passed as compile time preprocessor macros

Building the Library

You can build the MQTT Agent source files that are in the source directory, and add source/include to your compiler's include path. Additionally, the MQTT Agent library requires the coreMQTT library, whose files follow the same source/ and source/include pattern as the agent library; its build instructions can be found here.

If using CMake, the mqttAgentFilePaths.cmake file contains the above information of the source files and the header include path from this repository. The same information is found for coreMQTT from mqttFilePaths.cmake in the coreMQTT submodule.

For a CMake example of building the MQTT Agent library with the mqttAgentFilePaths.cmake file, refer to the coverity_analysis library target in test/CMakeLists.txt file.

Building Unit Tests

Checkout CMock Submodule

To build unit tests, the submodule dependency of CMock is required. Use the following command to clone the submodule:

git submodule update --checkout --init --recursive test/unit-test/CMock

Unit Test Platform Prerequisites

• For running unit tests
  • C90 compiler like gcc
  • CMake 3.13.0 or later
  • Ruby 2.0.0 or later is additionally required for the CMock test framework (that we use).
• For running the coverage target, gcov and lcov are additionally required.

Steps to build Unit Tests

1. Go to the root directory of this repository. (Make sure that the CMock submodule is cloned as described above)

2. Run the cmake command: cmake -S test -B build

3. Run this command to build the library and unit tests: make -C build all

4. The generated test executables will be present in build/bin/tests folder.

5. Run cd build && ctest to execute all tests and view the test run summary.

Reference examples

Please refer to the demos of the MQTT Agent library in the following locations for reference examples on FreeRTOS platforms:

Location
coreMQTT Agent Demos
FreeRTOS/FreeRTOS

Documentation

The MQTT Agent API documentation can be found here.

Generating documentation

The Doxygen references were created using Doxygen version 1.8.20. To generate the Doxygen pages yourself, please run the following command from the root of this repository:

doxygen docs/doxygen/config.doxyfile

Getting help

You can use your Github login to get support from both the FreeRTOS community and directly from the primary FreeRTOS developers on our active support forum. You can find a list of frequently asked questions here.

Contributing

See CONTRIBUTING.md for information on contributing.

License

This library is licensed under the MIT License. See the LICENSE file.