A blog by Devendra Tewari
This post shows how to use MQTT in Node-RED with brokers such as RabbitMQ and Mosquitto. The official Docker container image of Node-RED is used for convenience.
To run Node-RED Docker container
docker run -it -p 1880:1880 --name mynodered nodered/node-red-docker
If you kill the above shell and need to run the same container again
docker start -ai mynodered
You should now be able to create Node-RED flows at http://localhost:1880.
The first flow will be used to publish MQTT messages to the broker. Start with a new flow and add an inject node and an MQTT out node. Configure Payload in inject node to timestamp, to start after 1 second, and to repeat every 10 seconds. Configure MQTT out node next. Add new MQTT broker. Assuming MQTT broker is installed on your machine, set Server to localhost or 127.0.0.1. Set Port to 1883. Specify TLS and security settings if needed and finalize MQTT broker configuration. Specify Topic in MQTT out node as nodered/test and QoS as 2. Finalize node creation. Link inject node to MQTT out node.
The next flow will be used to subscribe to MQTT messages at the broker. Start with a new flow and add an MQTT in node and a debug node. Configure Server, Topic, and QoS of MQTT in node to the same values used in out node. Configure To in debug node to debug window. Link MQTT in node to debug node.
Deploy the flows.
Node-RED starts publishing timestamp values to the topic you configured, at 10 second intervals. It will also start receiving the values and showing them in the debug messages view.