Why MQTT is the IoT standard in IOT Protocols - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to publish a message to an MQTT topic.

IOT Protocols

client.publish('[1]', 'Hello IoT')

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

Asubscribe

Bconnect

Csensor/data

Ddisconnect

Attempts:

3 left

💡 Hint

Common Mistakes

Using connection commands instead of a topic name.

The publish method sends a message to the specified topic, here 'sensor/data'.

2fill in blank

medium

Complete the code to subscribe to an MQTT topic.

IOT Protocols

client.[1]('home/temperature')

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

Aconnect

Bpublish

Cdisconnect

Dsubscribe

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'publish' instead of 'subscribe'.

The subscribe method listens for messages on the given topic.

3fill in blank

hard

Fix the error in the MQTT connection code by completing the blank.

IOT Protocols

client.[1]('mqtt.example.com')

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

Aconnect

Bpublish

Csubscribe

Ddisconnect

Attempts:

3 left

💡 Hint

Common Mistakes

Trying to publish or subscribe before connecting.

The connect method establishes a connection to the MQTT broker.

4fill in blank

hard

Fill both blanks to create a dictionary of sensor readings filtered by temperature above 25.

IOT Protocols

{word: [1] for word in readings if readings[word] [2] 25}

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

Areadings[word]

B>

C<

Dword

Attempts:

3 left

💡 Hint

Common Mistakes

Using the key instead of the value.

Using wrong comparison operator.

This dictionary comprehension keeps readings where the temperature is greater than 25.

5fill in blank

hard

Fill all three blanks to create a dictionary with uppercase keys and values filtered by humidity less than 50.

IOT Protocols

{ [1]: [2] for [3] in data if data[[3]] < 50 }

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

Ak.upper()

Bdata[k]

Ck

Dv

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong variable names.

Not converting keys to uppercase.

This comprehension creates a dictionary with keys in uppercase and values from data where humidity is less than 50.

Practice

1. Why is MQTT considered ideal for small IoT devices?

easy

A. Because it only works with large devices

B. Because it requires a strong internet connection

C. Because it uses complex protocols for security

D. Because it uses very little power and is simple to implement

Solution

1. Step 1: Understand MQTT's design for IoT devices

   MQTT is designed to be lightweight and simple, which means it uses very little power and resources.

2. Step 2: Connect design to device needs

   Small IoT devices often have limited power and processing ability, so a simple, low-power protocol fits best.

3. Final Answer:

   Because it uses very little power and is simple to implement -> Option D

4. Quick Check:

   Low power + simplicity = Ideal for small IoT devices [OK]

Hint: MQTT is lightweight and simple, perfect for small devices [OK]

Common Mistakes:

• Thinking MQTT needs strong internet
• Assuming MQTT is complex
• Believing MQTT only works on big devices

2. Which of the following is the correct MQTT communication model?

easy

A. Client-server with direct device connections

B. Publish-subscribe with a broker in the middle

C. Peer-to-peer without any central server

D. Broadcast to all devices simultaneously

Solution

1. Step 1: Identify MQTT communication style

   MQTT uses a publish-subscribe model where devices publish messages to topics and subscribe to topics via a broker.

2. Step 2: Compare options to MQTT model

   Only the publish-subscribe with a broker matches MQTT's design; others describe different network models.

3. Final Answer:

   Publish-subscribe with a broker in the middle -> Option B

4. Quick Check:

   MQTT = Publish-subscribe + broker [OK]

Hint: MQTT always uses a broker for message routing [OK]

Common Mistakes:

• Confusing MQTT with direct client-server
• Thinking MQTT is peer-to-peer
• Assuming MQTT broadcasts messages

3. Given this MQTT scenario: A sensor publishes temperature data to topic home/temperature. A device subscribes to home/temperature. What will the subscribing device receive?

medium

A. All messages published to home/temperature

B. Only messages published to other topics

C. No messages unless it publishes first

D. Messages from unrelated topics

Solution

1. Step 1: Understand MQTT subscription behavior

   A device subscribing to a topic receives all messages published to that exact topic.

2. Step 2: Apply to given topic

   The device subscribed to home/temperature will get all messages published there, including the sensor's data.

3. Final Answer:

   All messages published to home/temperature -> Option A

4. Quick Check:

   Subscribe to topic = receive messages on that topic [OK]

Hint: Subscribe to a topic to get its messages [OK]

Common Mistakes:

• Thinking subscription needs publishing first
• Believing subscription gets unrelated topics
• Assuming no messages received without publishing

4. You wrote this MQTT client code but it never receives messages:

client.subscribe('home/lights')
client.publish('home/lights', 'ON')

What is the likely problem?

medium

A. MQTT does not support subscribing and publishing in the same client

B. The topic name is invalid and must be numeric

C. The client must connect to the broker before subscribing or publishing

D. The message payload must be a number, not a string

Solution

1. Step 1: Check MQTT client connection requirements

   MQTT clients must connect to the broker before subscribing or publishing messages.

2. Step 2: Analyze given code

   The code shows subscribe and publish calls but no connection step, so messages won't be received.

3. Final Answer:

   The client must connect to the broker before subscribing or publishing -> Option C

4. Quick Check:

   Connect first, then subscribe/publish [OK]

Hint: Always connect client to broker before actions [OK]

Common Mistakes:

• Thinking topic names must be numeric
• Believing one client can't subscribe and publish
• Assuming payload must be numeric

5. You want to design an IoT system that works reliably even when internet is unstable. Why is MQTT a good choice?

hard

A. Because MQTT uses a persistent session and small message size to handle weak connections

B. Because MQTT requires constant high-speed internet for real-time data

C. Because MQTT encrypts all messages by default without configuration

D. Because MQTT only works on local networks without internet

Solution

1. Step 1: Understand MQTT features for unstable networks

   MQTT supports persistent sessions and small message sizes, which help maintain communication despite weak or intermittent internet.

2. Step 2: Compare options to MQTT capabilities

   Because MQTT uses a persistent session and small message size to handle weak connections correctly describes MQTT's ability to handle weak connections; others are incorrect or unrelated.

3. Final Answer:

   Because MQTT uses a persistent session and small message size to handle weak connections -> Option A

4. Quick Check:

   Persistent sessions + small messages = reliable on weak internet [OK]

Hint: MQTT handles weak internet with persistent sessions [OK]

Common Mistakes:

• Assuming MQTT needs high-speed internet
• Thinking MQTT encrypts by default
• Believing MQTT only works locally