Automation - MQTT

Proven on:

19.3 / 20.3	4	11 (bullseye)	20.04.3	5.11
		(caveat)

Mosquitto MQTT Broker

As always...

Start with:

• sudo apt update
• sudo apt upgrade

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)

Note: Ubuntu repositories have an outdated version

If you want to know which version you've installed...

• mosquitto

(Ignore the error message "Error: Address already in use". It's already running as a service.)

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).

Debian / Version 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