[Solved] Given this MQTT subscription code on a Raspberry Pi, what will be printed when a message arrives?def on_message(client, userdata, msg): print(f"Topic: {msg.topic}, Message: {msg.payload.... | Raspberry Pi

Raspberry Pi - MQTT for IoT

Given this MQTT subscription code on a Raspberry Pi, what will be printed when a message arrives?

def on_message(client, userdata, msg):
    print(f"Topic: {msg.topic}, Message: {msg.payload.decode()}")

client.subscribe("home/livingroom/temperature")
client.on_message = on_message

ANo output because on_message is not called

BTopic: home/livingroom/temperature, Message: 22.5

CTopic: home/livingroom/temperature, Message: b'22.5'

DTopic: home/livingroom, Message: temperature

Step-by-Step Solution

Solution:

Step 1: Understand on_message callback
When a message arrives, on_message prints the topic and decoded payload string.
Step 2: Decode payload bytes to string
msg.payload.decode() converts bytes to string, so output shows readable message like '22.5'.
Final Answer:
Topic: home/livingroom/temperature, Message: 22.5 -> Option B
Quick Check:
Decoded payload prints as string, not bytes [OK]

Quick Trick: Decode payload bytes to string before printing [OK]

Common Mistakes:

MISTAKES

Printing raw bytes without decode
Confusing topic string
Assuming callback not triggered

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More Raspberry Pi Quizzes

Given this MQTT subscription code on a Raspberry Pi, what will be printed when a message arrives?

Step 1: Understand on_message callback

Step 2: Decode payload bytes to string

Final Answer:

Quick Check:

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