# 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/MISRAHome/MISRAC2012/tabid/196/Default.aspx).  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 and proof of functional correctness through the [CBMC automated reasoning tool](https://www.cprover.org/cbmc/).

See memory requirements for this library [here](https://docs.aws.amazon.com/embedded-csdk/202103.00/lib-ref/libraries/standard/coreMQTT/docs/doxygen/output/html/index.html#mqtt_memory_requirements).

**coreMQTT v1.1.0 [source code](https://github.com/FreeRTOS/coreMQTT/tree/v1.1.0/source) is part of the [FreeRTOS 202012.00 LTS](https://github.com/FreeRTOS/FreeRTOS-LTS/tree/202012.00-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.

## Sending metrics to AWS IoT

When establishing a connection with AWS IoT, users can optionally report the Operating System, Hardware Platform and MQTT client version information of their device to AWS. This information can help AWS IoT provide faster issue resolution and technical support. If users want to report this information, they can send a specially formatted string (see below) in the username field of the MQTT CONNECT packet.

Format

The format of the username string with metrics is:

```
<Actual_Username>?SDK=<OS_Name>&Version=<OS_Version>&Platform=<Hardware_Platform>&MQTTLib=<MQTT_Library_name>@<MQTT_Library_version>
```

Where

* <Actual_Username> is the actual username used for authentication, if username and password are used for authentication. When username and password based authentication is not used, this
is an empty value.
* <OS_Name> is the Operating System the application is running on (e.g. FreeRTOS)
* <OS_Version> is the version number of the Operating System (e.g. V10.4.3)
* <Hardware_Platform> is the Hardware Platform the application is running on (e.g. WinSim)
* <MQTT_Library_name> is the MQTT Client library being used (e.g. coreMQTT)
* <MQTT_Library_version> is the version of the MQTT Client library being used (e.g. 1.0.2)

Example

*  Actual_Username = “iotuser”, OS_Name = FreeRTOS, OS_Version = V10.4.3, Hardware_Platform_Name = WinSim, MQTT_Library_Name = coremqtt, MQTT_Library_version = 1.1.0. If username is not used, then “iotuser” can be removed.

```
/* Username string:
 * iotuser?SDK=FreeRTOS&Version=v10.4.3&Platform=WinSim&MQTTLib=coremqtt@1.1.0
 */

#define OS_NAME                   "FreeRTOS"
#define OS_VERSION                "V10.4.3"
#define HARDWARE_PLATFORM_NAME    "WinSim"
#define MQTT_LIB                  "coremqtt@1.1.0"

#define USERNAME_STRING           "iotuser?SDK=" OS_NAME "&Version=" OS_VERSION "&Platform=" HARDWARE_PLATFORM_NAME "&MQTTLib=" MQTT_LIB
#define USERNAME_STRING_LENGTH    ( ( uint16_t ) ( sizeof( USERNAME_STRING ) - 1 ) )

MQTTConnectInfo_t connectInfo;
connectInfo.pUserName = USERNAME_STRING;
connectInfo.userNameLength = USERNAME_STRING_LENGTH;
mqttStatus = MQTT_Connect( pMqttContext, &connectInfo, NULL, CONNACK_RECV_TIMEOUT_MS, pSessionPresent );
```


## Building the Library

The [mqttFilePaths.cmake](mqttFilePaths.cmake) file contains the information of all source files and the header include path required to build the MQTT library.

Additionally, the MQTT library requires two header files that are not part of the ISO C90 standard library, `stdbool.h` and `stdint.h`. For compilers that do not provide these header files, the [source/include](source/include) directory contains the files [stdbool.readme](source/include/stdbool.readme) and [stdint.readme](source/include/stdint.readme), which can be renamed to `stdbool.h` and `stdint.h`, respectively, to provide the type definitions required by MQTT.

As mentioned in the previous section, either a custom config file (i.e. `core_mqtt_config.h`) OR `MQTT_DO_NOT_USE_CUSTOM_CONFIG` macro needs to be provided to build the MQTT library.

For a CMake example of building the MQTT library with the `mqttFilePaths.cmake` file, refer to the `coverity_analysis` library target in [test/CMakeLists.txt](test/CMakeLists.txt) file.

## Building Unit Tests

### Checkout CMock Submodule
By default, the submodules in this repository are configured with `update=none` in [.gitmodules](.gitmodules) to avoid increasing clone time and disk space usage of other repositories (like [amazon-freertos](https://github.com/aws/amazon-freertos) that submodules this repository).

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
```

### 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](#checkout-cmock-submodule))

1. Run the *cmake* command: `cmake -S test -B build`

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

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

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

## Reference examples

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

| Platform | Location | Transport Interface Implementation |
| :-: | :-: | :-: |
| POSIX | [AWS IoT Device SDK for Embedded C](https://github.com/aws/aws-iot-device-sdk-embedded-C/tree/main/demos/mqtt) | POSIX sockets for TCP/IP and OpenSSL for TLS stack
| FreeRTOS | [FreeRTOS/FreeRTOS](https://github.com/FreeRTOS/FreeRTOS/tree/master/FreeRTOS-Plus/Demo) | FreeRTOS+TCP for TCP/IP and mbedTLS for TLS stack |
| FreeRTOS | [FreeRTOS AWS Reference Integrations](https://github.com/aws/amazon-freertos/tree/master/demos/coreMQTT) | Based on Secure Sockets Abstraction |


## Generating documentation

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

```shell
doxygen docs/doxygen/config.doxyfile
```

## Contributing

See [CONTRIBUTING.md](./.github/CONTRIBUTING.md) for information on contributing.
