Topic design patterns for IoT in IOT Protocols - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a topic pattern for device status updates.

IOT Protocols

topic = "devices/[1]/status"

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

Aupdate

Bdevice_id

Csensor

Dcommand

Attempts:

3 left

💡 Hint

Common Mistakes

Using generic words like 'update' or 'command' instead of device identifier.

The topic pattern uses device_id to specify which device's status is being updated.

2fill in blank

medium

Complete the code to subscribe to all temperature sensors in building 5.

IOT Protocols

topic = "building/5/[1]/temperature"

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

A+

Bdevice

C#

Dfloor

Attempts:

3 left

💡 Hint

Common Mistakes

Using multi-level wildcard # which matches too broadly.

The single-level wildcard + matches any sensor or device at that level in the topic hierarchy.

3fill in blank

hard

Fix the error in the topic pattern to correctly subscribe to all sensors in all buildings.

IOT Protocols

topic = "[1]/sensors/#"

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

A#

Bbuilding

C+

Dbuildings

Attempts:

3 left

💡 Hint

Common Mistakes

Using multi-level wildcard # which cannot appear except at the end of the topic.

The single-level wildcard + matches any building identifier, and # matches all subtopics under sensors.

4fill in blank

hard

Fill both blanks to create a topic pattern for commands sent to a specific device in a room.

IOT Protocols

topic = "[1]/[2]/commands"

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

Aroom

Bdevice

Csensor

Dbuilding

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping device and room or using sensor instead of device.

The pattern uses room and device to target commands to a specific device in a room.

5fill in blank

hard

Fill all three blanks to create a topic pattern for publishing sensor data with building, floor, and sensor type.

IOT Protocols

topic = "[1]/[2]/[3]/data"

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

Abuilding

Bfloor

Csensor

Ddevice

Attempts:

3 left

💡 Hint

Common Mistakes

Using device instead of sensor or wrong order of location levels.

The topic pattern includes building, floor, and sensor to organize sensor data hierarchically.

Practice

1. What is the main purpose of using topic design patterns in IoT communication?

easy

A. To increase the battery life of sensors

B. To encrypt messages for security

C. To reduce the size of IoT devices

D. To organize messages clearly and make communication scalable

Solution

1. Step 1: Understand the role of topics in IoT

   Topics help organize messages by categorizing them into levels separated by slashes.

2. Step 2: Identify the benefit of good topic design

   Good topic design makes communication clear and scalable, allowing easy message filtering and management.

3. Final Answer:

   To organize messages clearly and make communication scalable -> Option D

4. Quick Check:

   Topic design = Clear, scalable communication [OK]

Hint: Topics organize messages for clarity and scale [OK]

Common Mistakes:

• Confusing topic design with security features
• Thinking topic design affects device hardware
• Assuming topic design saves battery life

2. Which of the following is the correct syntax for a multi-level wildcard subscription in MQTT topics?

easy

A. home/#/temperature/+

B. home/temperature/+/+

C. home/+/temperature/#

D. home/temperature/#/+

Solution

1. Step 1: Recall MQTT wildcard rules

   The plus sign (+) matches one topic level, and the hash (#) matches multiple levels at the end.

2. Step 2: Check syntax correctness

   home/+/temperature/# uses + for one level and # at the end for multiple levels, which is valid syntax.

3. Final Answer:

   home/+/temperature/# -> Option C

4. Quick Check:

   Multi-level wildcard ends with # [OK]

Hint: Use + for single level, # only at end [OK]

Common Mistakes:

• Placing # in the middle of the topic
• Using + to match multiple levels
• Mixing order of + and # incorrectly

3. Given the subscription topic building/+/floor1/#, which published topic will NOT be received by the subscriber?

medium

A. building/roomC/floor2/temperature

B. building/roomB/floor1/humidity

C. building/room/floor1/temperature

D. building/roomA/floor1/temperature

Solution

1. Step 1: Analyze the subscription pattern

   The + matches exactly one level after 'building', and # matches any levels after 'floor1'.

2. Step 2: Test each published topic

   Options A, B, and C match 'building/roomX/floor1/...' correctly. building/roomC/floor2/temperature has 'floor2' instead of 'floor1', so it does not match.

3. Final Answer:

   building/roomC/floor2/temperature -> Option A

4. Quick Check:

   Subscription requires floor1 level [OK]

Hint: Check each topic level matches + and # rules [OK]

Common Mistakes:

• Ignoring the exact match required by + wildcard
• Assuming # matches levels before floor1
• Confusing floor1 and floor2 levels

4. Identify the error in this MQTT subscription topic: home/+/+/temperature/#/humidity

medium

A. The # wildcard is not allowed in the middle of the topic

B. Using multiple + wildcards consecutively is invalid

C. The topic must start with a slash

D. Wildcards cannot be combined with normal topic levels

Solution

1. Step 1: Review MQTT wildcard placement rules

   The # wildcard must be the last character in the topic filter and can only appear once.

2. Step 2: Check the given topic

   The # wildcard appears in the middle before /humidity, which is invalid syntax.

3. Final Answer:

   The # wildcard is not allowed in the middle of the topic -> Option A

4. Quick Check:

   # only at end of topic [OK]

Hint: # wildcard only at topic end [OK]

Common Mistakes:

• Thinking multiple + wildcards are invalid
• Believing topics must start with slash
• Assuming wildcards can't mix with normal levels

5. You want to design MQTT topics to monitor sensors in multiple buildings, floors, and rooms. Which topic pattern best supports scalable subscription to all temperature sensors on floor 2 across all buildings?

hard

A. building/+/+/floor2/temperature

B. building/+/floor2/+/temperature

C. building/#/floor2/temperature

D. building/+/floor2/temperature/#

Solution

1. Step 1: Understand the hierarchy needed

   Topics should include building, floor, room, and sensor type levels.

2. Step 2: Analyze each option for scalability and correctness

   building/+/floor2/+/temperature uses + to match any building and any room on floor2, then temperature sensor, which is clear and scalable. building/#/floor2/temperature misplaces # wildcard. building/+/+/floor2/temperature has extra + before floor2, which breaks hierarchy. building/+/floor2/temperature/# places # after temperature, which is unnecessary and less clear.

3. Final Answer:

   building/+/floor2/+/temperature -> Option B

4. Quick Check:

   Use + for flexible levels, keep clear order [OK]

Hint: Use + for each flexible level, keep order clear [OK]

Common Mistakes:

• Misplacing # wildcard inside topic
• Adding extra + levels breaking hierarchy
• Using # after sensor type unnecessarily