paho-mqtt library usage in Raspberry Pi - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the main purpose of the paho-mqtt library?

The paho-mqtt library helps devices like Raspberry Pi send and receive messages using the MQTT protocol, which is a simple way for devices to talk to each other over the internet.

beginner

How do you connect a Raspberry Pi client to an MQTT broker using paho-mqtt?

You create a client object, then use the connect() method with the broker's address and port to connect. For example: <br>client = mqtt.Client()<br>client.connect('broker.hivemq.com', 1883)

intermediate

What is the role of the on_message callback in paho-mqtt?

The on_message callback is a function you define to handle messages that arrive on topics you subscribed to. It runs automatically when a new message comes in.

beginner

How do you subscribe to a topic using paho-mqtt?

After connecting, you call client.subscribe('topic/name') to listen for messages sent to that topic.

beginner

What method do you use to send a message to a topic with paho-mqtt?

Use client.publish('topic/name', 'message') to send a message to the MQTT broker on the chosen topic.

Which method connects your Raspberry Pi client to the MQTT broker?

A connect()

B subscribe()

C publish()

D loop_forever()

The connect() method establishes the connection to the MQTT broker.

What does the subscribe() method do in paho-mqtt?

A Sends a message to a topic

B Connects to the broker

C Stops the client

D Listens for messages on a topic

subscribe() tells the client to listen for messages on a specific topic.

Which callback function handles incoming messages?

A on_connect

B on_message

C on_publish

D on_disconnect

on_message is called when a new message arrives on a subscribed topic.

What is the purpose of client.loop_forever()?

A To keep the client running and processing network events

B To disconnect from the broker

C To publish messages repeatedly

D To subscribe to multiple topics

loop_forever() keeps the client active to send and receive messages.

How do you publish a message 'Hello' to topic 'test/topic'?

A client.connect('test/topic', 'Hello')

B client.subscribe('test/topic', 'Hello')

C client.publish('test/topic', 'Hello')

D client.loop('test/topic', 'Hello')

publish() sends the message 'Hello' to the specified topic.

Explain the basic steps to set up a Raspberry Pi client using paho-mqtt to receive messages.

Think about how the client connects, listens, and reacts to messages.

Describe how to send a message from Raspberry Pi to an MQTT topic using paho-mqtt.

Focus on connection and publishing steps.