Mosquitto

Installation

On Debian-based systems the MQTT broker and MQTT clients can be installed as follows:

apt install mosqutto mosqutto-clients

On Arch-based systems the MQTT broker and MQTT clients can be installed as follows:

pacman -S mosquitto

Post Installation

In order to enable the MQTT broker so it starts on every boot, we have to enable it via systemctl:

systemctl enable mosquitto.service 

For starting the service run:

systemctl start mosquitto.service 

Systemd Commands

Command	Description
systemctl start mosquitto.service	Start the mosquitto service
systemctl restart mosquitto.service	Restart the mosquitto service
systemctl reload mosquitto.service	Reload the mosquitto service configuration
systemctl stop mosquitto.service	Stop the mosquitto service
systemctl status mosquitto.service	Service status of mosquitto
systemctl disable mosquitto.service	Disable the mosquitto service
systemctl enable mosquitto.service	Enable the mosquitto service

Simple Testing

Now that we have installed Mosquitto, it is time to test the Mosquitto broker. Fortunately, testing MQTT, once it is installed, is pretty simple thanks to the MQTT command line tools. Here, we can use the mosquitto clients mosquitto_sub and mosquitto_pub to send and receive messages.

With the command mosquitto_sub, we can create a MQTT subscriber that listens to specific topics. For instance, the command below starts a MQTT subscriber that listens to the topic home/# and the sub-topics like home/kitchen. The symbol # in the topic home/# is a multi-level wildcard that matches topics like home, home/kitchen, home/kitchen/temperature, and so on.

mosquitto_sub -h zeus.internal -t "home/#" -v

For sending messages, like JSON strings, we can leverage the mosquitto_pub client. As the command below shows, we start a MQTT publisher that publishes once the JSON message '{ "temperature":"..." }' to the topic "home".

mosquitto_pub -h zeus.internal -t "home" -m '{ "measurement": {"value": 25.0, "unit": "Celsius" } }'