Automation - MQTT

Proven on:

	12 (bookworm)	(caveat)
	4	(caveat)
	19.3 / 20.3
	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?

(Tho... If you want the latest & gratest and you're feeling adventurous... There's a CopyPasta page here.)

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Note: Ubuntu repositories have an outdated version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...

• sudo 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

(Ignore this if you built from source. It's apparently a repo thing...)

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

Securing the broker

Reference

Mosquitto supports password authentication...

Simplest is:

password Authentication

You can create a password file by:

• sudo mosquitto_passwd -c /etc/mosquitto/SecretSquirrels USERNAME

Then edit the configuration:

• sudo vi /etc/mosquitto/mosquitto.conf

and replace allow_anonymous true with password_file /etc/mosquitto/SecretSquirrels

Then restart the broker:

• sudo service mosquitto restart

From this point, you have to provide USERNAME & PASSWORD to access it.

Note:

The password file must be able to be read by whatever user Mosquitto is running as. On Linux/POSIX systems this will typically be the mosquitto user, and /etc/mosquitto/password_file is a good place for the file itself.