MQTT and Mosquitto

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Installation packages

On Raspberry PI 5 (running 64bit OS) Paho Mqtt can be installed with C++ support. This failed on Raspberry pi 4 (running 32 bit OK - due to Lidar support for YD Lidar S4B).

However, the C interface API works on Raspberry 32bit OS (Bullseye).

Install on 64bit OS:

sudo apt install libpaho-mqtt-dev libpaho-mqttpp-dev mosquitto-dev mosquitto-clients mosquitto

Install on 32bit OS:

sudo apt install libpaho-mqtt-dev mosquitto-dev mosquitto-clients mosquitto

- in addition to other packages required for normal compile

This should allow the teensy interface to compile.

Documentation MQTT API

For Paho-mqtt on Python, see https://eclipse.dev/paho/files/paho.mqtt.python/html/index.html

For C interface: https://eclipse.github.io/paho.mqtt.c/MQTTClient/html/index.html

For C++ see: https://eclipse.dev/paho/files/cppdoc/classmqtt_1_1client.html

Configure Mosquitto

Copy the full option list example to /etc/mosquitto/conf.d/:

 sudo cp /usr/share/doc/mosquitto/examples/mosquitto.conf /etc/mosquitto/conf.d/

Uncomment and change in the 'listener' group:

#listener
listener 1883

In the security group:

#allow_anonymous false
allow_anonymous true

Restart mosquitto to take effect.

sudo service mosquitto restart

Test available messages

The mosquito_sub too allow display of messages, e.g.:

mosquitto_sub -h localhost -t robobot/drive/# -d

This will subscribe to messages from system robobot, function drive and all topics in this function (the '#' is wildcard for the rest).

The -d option is for debug and shows full topic and other information.

The mosquitto_pub allow test messages to be send, e.g.:

mosquitto_pub -h localhost -t robobot/drive/T0/go -m "3 3" -q 2

The message is "3 3" and the service quality 2 (send exactly 1 time)