Wildcard subscriptions (+ and #) in IOT Protocols - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to subscribe to all topics under 'home/kitchen' using a single-level wildcard.

IOT Protocols

client.subscribe("home/kitchen/[1]")

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

A*

B#

C+

D/

Attempts:

3 left

💡 Hint

Common Mistakes

Using '#' instead of '+' subscribes to all subtopics recursively, not just one level.

The single-level wildcard '+' matches exactly one topic level. So 'home/kitchen/+' subscribes to all topics directly under 'home/kitchen'.

2fill in blank

medium

Complete the code to subscribe to all topics under 'home' recursively using a multi-level wildcard.

IOT Protocols

client.subscribe("home/[1]")

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

A#

B+

C*

D/

Attempts:

3 left

💡 Hint

Common Mistakes

Using '+' instead of '#' subscribes only to one level, missing deeper topics.

The multi-level wildcard '#' matches any number of topic levels, including zero. So 'home/#' subscribes to all topics under 'home' and its subtopics recursively.

3fill in blank

hard

Fix the error in the subscription to match all topics under 'office' and its subtopics.

IOT Protocols

client.subscribe("office/[1]")

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

A+/#

B+

C#/+

D#

Attempts:

3 left

💡 Hint

Common Mistakes

Placing '#' in the middle of the topic filter causes syntax errors.

The multi-level wildcard '#' must be at the end of the topic filter and matches all subtopics. 'office/#' correctly subscribes to all topics under 'office'.

4fill in blank

hard

Fill both blanks to subscribe to all sensors in any room under 'building1'.

IOT Protocols

client.subscribe("building1/[1]/[2]")

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

A+

Bsensors

C#

Droom

Attempts:

3 left

💡 Hint

Common Mistakes

Using '#' in the middle of the topic filter is invalid.

'building1/+/sensors' subscribes to the sensors topic in any room ('+') under 'building1'. Using '+' wildcard for room names and 'sensors' as the topic name is correct.

5fill in blank

hard

Fill all three blanks to subscribe to all temperature readings in any floor and any room under 'campus'.

IOT Protocols

client.subscribe("campus/[1]/[2]/[3]")

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

A+

Btemperature

Dfloor

Attempts:

3 left

💡 Hint

Common Mistakes

Using '#' instead of '+' for room level subscribes too broadly.

'campus/+/+/temperature' subscribes to temperature readings in any room ('+') on any floor ('+') under 'campus'.