Subscribing to control commands in IOT Protocols - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to subscribe to the control topic using MQTT.

IOT Protocols

client.subscribe('[1]')

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

Acontrol/commands

Bdata/updates

Csensor/readings

Dalerts/warnings

Attempts:

3 left

💡 Hint

Common Mistakes

Subscribing to a data or sensor topic instead of the control topic.

Using an incorrect topic string with typos.

The control commands are sent on the control/commands topic, so subscribing to this topic allows the device to receive control messages.

2fill in blank

medium

Complete the code to set the callback function for incoming control messages.

IOT Protocols

client.on_message = [1]

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

Ahandle_data

Bprocess_sensor

Chandle_control

Don_connect

Attempts:

3 left

💡 Hint

Common Mistakes

Assigning the wrong callback function that does not handle control commands.

Confusing the on_connect callback with on_message.

The callback function handle_control is designed to process incoming control commands.

3fill in blank

hard

Fix the error in the subscription quality of service (QoS) level to ensure reliable delivery.

IOT Protocols

client.subscribe('control/commands', qos=[1])

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A1

B3

C-1

D0

Attempts:

3 left

💡 Hint

Common Mistakes

Using an invalid QoS value like 3 or -1.

Using QoS 0 which may lose messages.

QoS level 1 ensures that the message is delivered at least once, which is suitable for control commands.

4fill in blank

hard

Fill both blanks to correctly initialize the MQTT client and connect to the broker.

IOT Protocols

client = mqtt.Client([1])
client.connect([2], 1883, 60)

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A'device123'

B'broker.example.com'

C'control/commands'

D'user1'

Attempts:

3 left

💡 Hint

Common Mistakes

Using a topic name as client ID or broker address.

Using username instead of client ID.

The client ID should be a unique identifier like 'device123'. The broker address is the server to connect to, here 'broker.example.com'.

5fill in blank

hard

Fill all three blanks to create a subscription with a callback that prints the received control command payload.

IOT Protocols

def [1](client, userdata, message):
    print('Received command:', message.[2].decode())

client.subscribe('control/commands', qos=1)
client.on_message = [3]

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

Ahandle_control

Bpayload

Dtopic

Attempts:

3 left

💡 Hint

Common Mistakes

Using different names for the function and callback assignment.

Accessing message.topic instead of message.payload for the command data.

The function handle_control processes messages. The payload contains the message data, which must be decoded. The callback is assigned to handle_control.