MQTT Raspberry Pi

The broker is primarily responsible for receiving all messages, filtering the messages, decide who is interested in it and then publishing the message to all subscribed clients.

Installing Mosquitto Broker on Raspbian OS

https://randomnerdtutorials.com/how-to-install-mosquitto-broker-on-raspberry-pi/

Test MQTT Broker Installation

https://randomnerdtutorials.com/testing-mosquitto-broker-and-client-on-raspbbery-pi/

Another site

https://appcodelabs.com/introduction-to-iot-build-an-mqtt-server-using-raspberry-pi