0302-06 Node-RED MQTT

Example Projects > 0302 IoT Integrations > 0302-06 Node-RED MQTT

Node-RED + MQTT example

The source files located in this folder illustrate how to communicate with REXYGEN REST API using popular tool Node-red and MQTT communication protocol in order to pass data from the REXYGEN to devices listening on the MQTT topic and vica versa to store data flowing from the MQTT topic in the REXYGEN.

In the nodered_flow.txt file is a flow of nodes which represents configuration of the Node-RED framework. The node named as GET data from REXYGEN API is set up to receive value of the CNR_OUT block. This value is then passed to the MQTT topic in the node rex_topic output node. There is also an rex_topic input node that is listening to the same topic and is therefor notified with all the values that flow through the topic. Every value is then passed to the CNR_IN block in the POST data to REXYGEN API.

Nodes Parse data are simple functions that preproccess data for the REXYGEN API requests.


Nodes that communicate with the REST API are required to use basic authentification that can be set in the properties of the block.

Timing of the project

The algorithm runs each 5 seconds. Edit the Clock node in the flow for different timing options.


  • Node.js and Node-RED must be installed and running on the target (e.g.:Debian Jessie - apt-get install nodered will install all required packages).
  • REXYGEN Runtime Core must be installed and running on the target device.

Running the example

  • The *exec.mdl file is the project main file.
  • Open it with REXYGEN Studio.
  • Compile and download it to the target device.
  • Start node-red on the target and use web browser to navigate to the address of the node-red's webserver. (default address is
  • Import flow from OpenWeatherMapAPI_flow.txt. You can use either import from clipboard or you can copy the file to the /lib/flows in your installation and then import the flow as a Library.
  • Open the Get weather info node and specify your unique OpenWeatherMap API ID in parameter URL: http://api.openweathermap.org/data/2.5/weather?q=Pilsen&units=metric&appid=your_API_ID
  • Open nodes with POST requests and Get CNDR heating curve node with GET request from the REXYGEN and specify target URL with corresponding credentials.
  • Deploy the flow. If everything is done correctly you should see data about the weather stored in the REXYGEN execution and as a result of GET request you should see adequate supply water temperature printed in the debug console of Node-RED.


Additional information

  • Visit the REXYGEN webpage for more information about the example projects and developing advanced automation and control solutions using REXYGEN.