Question $1$Figure $3$: Basic working of MaTT

The four widely accepted and emerging messaging protocols for IoT systems are: MQTT$,$ CoAP, AMQP, and HTTP$,$ however, the most widely used protocol is MQTT$.$ MQTT is a publish$-$subscribe$-$based messaging protocol used on the Internet of Things. It works on top of the TCP$/$IP protocol and is used for connections with remote locations in which a "small code footprint" is required, or limited network bandwidth. The basic working is shown in attached figure.

A$)$ In relation to the messaging protocol for IoT, briefly explain the following terms with examples:

$$ Broker

$$ Client

$$ Topic

$$ Publish

$$ Subscribe

$$ QoS

B$)$ Explain the working of MQTT with any relevant examples.