## coreMQTT Client Library

This repository contains the coreMQTT library that has been optimized for a low memory footprint.  The coreMQTT library is compliant with the [MQTT 3.1.1](https://docs.oasis-open.org/mqtt/mqtt/v3.1.1/mqtt-v3.1.1.html) standard.  It has no dependencies on any additional libraries other than the standard C library, a customer-implemented network transport interface, and *optionally* a user-implemented platform time function.  This library is distributed under the [MIT Open Source License](LICENSE).

This library has gone through code quality checks including verification that no function has a [GNU Complexity](https://www.gnu.org/software/complexity/manual/complexity.html) score over 8, and checks against deviations from mandatory rules in the [MISRA coding standard](https://www.misra.org.uk).  Deviations from the MISRA C:2012 guidelines are documented under [MISRA Deviations](MISRA.md). This library has also undergone both static code analysis from [Coverity static analysis](https://scan.coverity.com/), and validation of memory safety through the [CBMC automated reasoning tool](https://www.cprover.org/cbmc/).

See memory requirements for this library [here](./docs/doxygen/include/size_table.md).

**coreMQTT v2.1.1 [source code](https://github.com/FreeRTOS/coreMQTT/tree/v2.1.1/source) is part of the [FreeRTOS 202210.01 LTS](https://github.com/FreeRTOS/FreeRTOS-LTS/tree/202210.01-LTS) release.**

## MQTT Config File

The MQTT client library exposes build configuration macros that are required for building the library.
A list of all the configurations and their default values are defined in [core_mqtt_config_defaults.h](source/include/core_mqtt_config_defaults.h). 
To provide custom values for the configuration macros, a custom config file named `core_mqtt_config.h` can be
provided by the application to the library.

By default, a `core_mqtt_config.h` custom config is required to build the library. To disable this requirement
and build the library with default configuration values, provide `MQTT_DO_NOT_USE_CUSTOM_CONFIG` as a compile time preprocessor macro.

**Thus, the MQTT library can be built by either**:
* Defining a `core_mqtt_config.h` file in the application, and adding it to the include directories list of the library  
**OR**
* Defining the `MQTT_DO_NOT_USE_CUSTOM_CONFIG` preprocessor macro for the library build.

## Documentation

For pre-generated documentation, please see the documentation linked in the locations below:

| Location |
| :-: |
| [FreeRTOS.org](https://freertos.org/Documentation/api-ref/coreMQTT/docs/doxygen/output/html/index.html) |

Note that the latest included version of coreMQTT may differ across repositories.