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Gemini : How to set MQTT communication

Gemini : How to set MQTT communication

Owned by Jérôme Hahang, created
Last updated: May 27, 2025

Procedure to quickly establish a MQTT communication between Gemini and the MQTT broker, and then subscribe to a MQTT topic to receive messages that are posted by Gemini to the broker.

The MQTT Broker used here is the open-source message broker Eclipse Mosquitto. It will be installed on a laptop.

 Instructions

 

  1. Installing Mosquitto on your machine

  • On MacOS

    • brew install mosquitto

    • Check the mosquitto service is started

brew services list

  • On Linux

    • sudo apt install mosquitto mosquitto-clients

    • Check the mosquitto service is started

    • sudo systemctl start mosquitto

    • enable the service to be ran at startup.

    • sudo systemctl enable mosquitto

  • Configure Mosquitto to allow :

    • connections without credentials

    • Listen to port 1883 on every ethernet interfaces available:

sudo nano /etc/mosquitto/mosquitto.conf (for mac : /opt/homebrew/etc/mosquitto/mosquitto.conf./)

Add/uncomment the following lines

allow_anonymous true listener 1883 0.0.0.0

then restart the mosquitto service

sudo systemctl restart mosquitto (Linux) brew services start mosquitto (macos)

 

Now the broker is set up to allow any connections without credentials and to listen to port 1883 on any ethernet interfaces available.

Specify the interface IP instead of 0.0.0.0, if you want mosquitto to listen a specific interface

 

 

  1. Configuring Gemini to post data to the MQTT broker

In Gemini → Settings Tab → Lidar Hub, under mqtt_publishers section :

image-20250527-133337.png

  • Source : Select only one source at a time. eg: source: object_list, if more source is required duplicate the MQTT publisher and select different source.

  • Host : IP on the machine where the MQTT broker is installed

Example of my own settings :

image-20250527-133724.png

 

 

  1. Check with Wireshark than Gemini sends data over the network to the broker IP

image-20250527-135501.png

 

 

  1. Subscribe to a broker topic to get data posted by Gemini with the GUI MQTT Explorer.

  • Navigate to MQTT Explorer and download MQTT Explorer

  • Create a new connection using your broker IP

image-20250527-140600.png
Here in the example, the broker is installed in my laptop, this is why the host is localhost

 

image-20250527-140815.png

You should see the incoming messages refreshed once per second.