mqtt_client

</a> </a>

The mqtt_client package provides a ROS 2 component node that enables connected ROS-based devices or robots to exchange ROS messages via an MQTT broker using the MQTT protocol. This works generically for arbitrary ROS message types. The mqtt_client can also exchange primitive messages with MQTT clients running on devices not based on ROS.

[!IMPORTANT]
This repository is open-sourced and maintained by the Institute for Automotive Engineering (ika) at RWTH Aachen University.
V2X Communication is one of many research topics within our Vehicle Intelligence & Automated Driving domain.
If you would like to learn more about how we can support your automated driving or robotics efforts, feel free to reach out to us!
:email: opensource@ika.rwth-aachen.de

• Installation
  • docker-ros
• Usage
  • Quick Start
  • Launch
  • Configuration
• Primitive Messages
• Latency Computation
• Package Summary
• Acknowledgements

Installation

The mqtt_client package is released as an official ROS 2 package and can easily be installed via a package manager.

sudo apt update
sudo apt install ros-$ROS_DISTRO-mqtt-client

If you would like to install mqtt_client from source, simply clone this repository into your ROS 2 workspace. All dependencies that are listed in the ROS package.xml can be installed using rosdep.

# mqtt_client$
rosdep install -r --ignore-src --from-paths .

# workspace$
colcon build --packages-up-to mqtt_client --cmake-args -DCMAKE_BUILD_TYPE=Release

docker-ros

mqtt_client is also available as a Docker image, containerized through docker-ros.

docker run --rm ghcr.io/ika-rwth-aachen/mqtt_client:latest # or distro-specific tags, e.g., :rolling

Usage

The mqtt_client can be easily integrated into an existing ROS-based system. Below, you first find a quick start guide to test the mqtt_client on a single machine. Then, more details are presented on how to launch and configure it in more complex applications.

Quick Start

Follow these steps to quickly launch a working mqtt_client that is sending ROS messages via an MQTT broker to itself.

Demo Broker

It is assumed that an MQTT broker (such as Mosquitto) is running on localhost:1883.

For this demo, you may easily launch Mosquitto with its default configuration using Docker.

docker run --rm --network host --name mosquitto eclipse-mosquitto

For a more advanced setup of your own broker, check out our instructions for running an MQTT broker in Docker with enabled authentication and encryption here.

Demo Configuration

The mqtt_client is best configured with a ROS parameter yaml file. The configuration shown below (also see params.yaml / params.yaml) allows an exchange of messages as follows:

• ROS messages received locally on ROS topic /ping/ros are sent to the broker on MQTT topic pingpong/ros;
• MQTT messages received from the broker on MQTT topic pingpong/ros are published locally on ROS topic /pong/ros;
• primitive ROS messages received locally on ROS topic /ping/primitive are sent as primitive (string) messages to the broker on MQTT topic pingpong/primitive;
• MQTT messages received from the broker on MQTT topic pingpong/primitive are published locally as primitive ROS messages on ROS topic /pong/primitive.

```yaml broker: host: localhost port: 1883 bridge: ros2mqtt: - ros_topic: /ping/ros mqtt_topic: pingpong/ros - ros_topic: /ping/primitive mqtt_topic: pingpong/primitive primitive: true mqtt2ros: - mqtt_topic: pingpong/ros

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