abawchen/ros-mqtt-bridge-example

Environment

• Ubuntu 18.04
• Python 2.7.15
• ROS: melodic

Quick start

Installation

$ sudo apt install ros-melodic-rosbridge-server

prepare MQTT broker and client

$ sudo apt-get install mosquitto mosquitto-clients

Install python modules

$ pip install -r requirements.txt

launch node

$ roslaunch mqtt_bridge demo.launch

# with tls options
$ roslaunch mqtt_bridge demo.launch use_tls:=True

Publish to /ping,

$ rostopic pub /ping std_msgs/Bool "data: true"

and see response to /pong.

$ rostopic echo /pong
data: True
---

Publish "hello" to /echo,

$ rostopic pub /echo std_msgs/String "data: 'hello'"

and see response to /back.

$ rostopic echo /back
data: hello
---

You can also see MQTT messages using mosquitto_sub

$ mosquitto_sub -t '#'

Usage

parameter file (config.yaml):

mqtt:
  client:
    protocol: 4      # MQTTv311
  connection:
    host: localhost
    port: 1883
    keepalive: 60
bridge:
  # ping pong
  - factory: mqtt_bridge.bridge:RosToMqttBridge
    msg_type: std_msgs.msg:Bool
    topic_from: /ping
    topic_to: ping
  - factory: mqtt_bridge.bridge:MqttToRosBridge
    msg_type: std_msgs.msg:Bool
    topic_from: ping
    topic_to: /pong

launch file:

<launch>
  <node name="mqtt_bridge" pkg="mqtt_bridge" type="mqtt_bridge_node.py" output="screen">
    <rosparam file="/path/to/config.yaml" command="load" />
  </node>
</launch>

Configuration

mqtt

Parameters under mqtt section are used for creating paho's mqtt.Client and its configuration.

subsections

• client: used for mqtt.Client constructor
• tls: used for tls configuration
• account: used for username and password configuration
• message: used for MQTT message configuration
• userdata: used for MQTT userdata configuration
• will: used for MQTT's will configuration

See mqtt_bridge.mqtt_client for detail.

mqtt private path

If mqtt/private_path parameter is set, leading ~/ in MQTT topic path will be replaced by this value. For example, if mqtt/pivate_path is set as "device/001", MQTT path "~/value" will be converted to "device/001/value".

serializer and deserializer

mqtt_bridge uses json as a serializer in default. But you can also configure other serializers. For example, if you want to use messagepack for serialization, add following configuration.

serializer: msgpack:dumps
deserializer: msgpack:loads

bridges

You can list ROS <--> MQTT tranfer specifications in following format.

bridge:
  # ping pong
  - factory: mqtt_bridge.bridge:RosToMqttBridge
    msg_type: std_msgs.msg:Bool
    topic_from: /ping
    topic_to: ping
  - factory: mqtt_bridge.bridge:MqttToRosBridge
    msg_type: std_msgs.msg:Bool
    topic_from: ping
    topic_to: /pong

• factory: bridge class for transfering message from ROS to MQTT, and vise versa.
• msg_type: ROS Message type transfering through the bridge.
• topic_from: topic incoming from (ROS or MQTT)
• topic_to: topic outgoing to (ROS or MQTT)

Also, you can create custom bridge class by inheriting mqtt_brige.bridge.Bridge.

License

This software is released under the MIT License, see LICENSE.txt.