Retained messages in IOT Protocols - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to publish a retained message in MQTT.

IOT Protocols

client.publish('home/temperature', '22', retain=[1])

Drag options to blanks, or click blank then click option'

AFalse

B0

CNone

DTrue

Attempts:

3 left

💡 Hint

Common Mistakes

Using retain=False will not keep the message for new subscribers.

Setting retain=True tells the broker to keep the message for new subscribers.

2fill in blank

medium

Complete the code to subscribe to a topic and receive retained messages.

IOT Protocols

client.subscribe('[1]')

Drag options to blanks, or click blank then click option'

Ahome/temperature

Bhome/temperature/last

Chome/temperature/retained

Dhome/temperature/#

Attempts:

3 left

💡 Hint

Common Mistakes

Using wildcards may not receive the retained message as expected.

Subscribing to the exact topic home/temperature receives retained messages if any exist.

3fill in blank

hard

Fix the error in the code to clear a retained message by publishing an empty payload.

IOT Protocols

client.publish('home/temperature', [1], retain=True)

Drag options to blanks, or click blank then click option'

A0

BNone

C''

D' '

Attempts:

3 left

💡 Hint

Common Mistakes

Using None or a space character does not clear the retained message.

Publishing an empty string '' with retain=True clears the retained message.

4fill in blank

hard

Fill both blanks to create a retained message dictionary with topic and payload.

IOT Protocols

{'topic': '[1]', 'payload': '[2]'}

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Ahome/temperature

B22

Chome/humidity

D45

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping topic and payload values or using incorrect topic names.

The dictionary keys topic and payload hold the topic name and message content respectively.

5fill in blank

hard

Fill all three blanks to filter retained messages with payload greater than 20.

IOT Protocols

retained_msgs = {msg['topic']: msg['payload'] for msg in messages if int(msg['payload']) [1] [2] and msg.get('retain', False) == [3]

Drag options to blanks, or click blank then click option'

A>

B20

CTrue

DFalse

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong comparison operators or checking retain flag incorrectly.

This comprehension filters messages where payload is greater than 20 and the message is retained.