Automation - MQTT

• Proven on Mint [19.3]
• Proven on SparkyLinux [5.11]
• Proven on raw Debian [11 - bullseye] (With a caveat)
• Proven on raw Ubuntu [20.04.3 LTS]

Mosquitto MQTT Broker

Installing Mosquitto

• sudo apt-get install mosquitto

Pretty simple, eh?

Ensure that Mosquitto broker is running

• sudo service mosquitto status

expected result is Active: active (running)

Debian Caveat

During an install on a raw Debian system, I discovered that Mosquitto refused connection when I tried to access it with anything other than "localhost" as the hostname...

Apparently, mosquitto 2.0 binds only to the loopback interface unless specifically told otherwise.

& Debian installs v2.0 or higher...

But for now, It's a simple matter of editing the config file for Mosquitto.

• sudo vi /etc/mosquitto/mosquitto.conf

& add in:

listener 1883
allow_anonymous true

Then,

• sudo service mosquitto restart

Install client tools for testing etc

(Do this on any machine expected to manually use MQTT)

• sudo apt install mosquitto-clients

Testing

In a terminal:

• mosquitto_sub -h localhost -t "mqtt" -v

In another terminal:

• mosquitto_pub -h localhost -t "mqtt" -m "Hello MQTT"

Now the message “mqtt Hello MQTT” will be displayed in the first terminal where the topic “mqtt” is subscribed.

Subscribing to # gives you a subscription to everything except for topics that start with a $ (these are normally control topics anyway).