Topic design patterns for IoT in IOT Protocols - Step-by-Step Execution

Process Flow - Topic design patterns for IoT

Device publishes data

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Broker receives message

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Broker applies topic pattern

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Subscribers receive messages based on topic

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Data processed or acted upon

This flow shows how IoT devices send data to a broker, which uses topic design patterns to route messages to subscribers.

Execution Sample

IOT Protocols

Device publishes to topic: home/kitchen/temperature
Subscriber subscribes to: home/+/temperature
Broker routes message to subscriber

A device sends temperature data from the kitchen. The subscriber listens to all rooms' temperature using a wildcard in the topic.

Process Table

Step	Action	Topic Published	Subscriber Topic Filter	Match Result	Message Delivered
1	Device publishes data	home/kitchen/temperature	home/+/temperature	Match	Yes
2	Device publishes data	home/livingroom/humidity	home/+/temperature	No Match	No
3	Device publishes data	home/kitchen/humidity	home/+/humidity	Match	Yes
4	Device publishes data	office/kitchen/temperature	home/+/temperature	No Match	No
5	Device publishes data	home/kitchen/temperature	home/#	Match	Yes

💡 All published messages processed; routing based on topic pattern matching completed.

Status Tracker

Variable	Start	After 1	After 2	After 3	After 4	After 5
Topic Published		home/kitchen/temperature	home/livingroom/humidity	home/kitchen/humidity	office/kitchen/temperature	home/kitchen/temperature
Subscriber Topic Filter	home/+/temperature	home/+/temperature	home/+/temperature	home/+/humidity	home/+/temperature	home/#
Match Result		Match	No Match	Match	No Match	Match
Message Delivered		Yes	No	Yes	No	Yes

Key Moments - 3 Insights

Why does 'home/livingroom/humidity' not match 'home/+/temperature'?

Because the subscriber's topic filter expects 'temperature' as the last part, but the published topic ends with 'humidity' (see execution_table row 2).

What does the '+' wildcard represent in topic filters?

It matches exactly one level in the topic hierarchy, so 'home/+/temperature' matches any single word between 'home' and 'temperature' (see execution_table rows 1 and 2).

How does the '#' wildcard differ from '+' in topic filters?

'#' matches any number of levels including zero, so 'home/#' matches all topics starting with 'home' regardless of depth (see execution_table row 5).

Visual Quiz - 3 Questions

Look at the execution table, which published topic matches the subscriber filter 'home/+/humidity'?

A office/kitchen/temperature

B home/livingroom/humidity

C home/kitchen/humidity

D home/kitchen/temperature

💡 Hint

Check the 'Subscriber Topic Filter' and 'Match Result' columns in execution_table row 3.

At which step does the message get delivered despite the topic having multiple levels after 'home'?

A Step 5

B Step 2

C Step 4

D Step 3

💡 Hint

Look at the '#' wildcard usage in the subscriber filter in execution_table row 5.

If the subscriber filter changes from 'home/+/temperature' to 'home/kitchen/temperature', which published topics will match?

A All topics with 'temperature' at the end

B Only 'home/kitchen/temperature'

C All topics starting with 'home'

D No topics will match

💡 Hint

Exact topic filters match only identical topics, unlike wildcards (see variable_tracker Subscriber Topic Filter changes).

Concept Snapshot

IoT topic design patterns use hierarchical strings separated by '/' to organize messages.
Wildcards '+' matches one level; '#' matches multiple levels.
Devices publish to topics; subscribers receive messages matching their topic filters.
This pattern enables flexible, scalable message routing in IoT systems.

Full Transcript

In IoT systems, devices send messages to a broker using topics structured like paths with levels separated by slashes. Subscribers listen to topics using filters that can include wildcards: '+' for one level and '#' for multiple levels. The broker matches published topics to subscriber filters and delivers messages accordingly. For example, a device publishing to 'home/kitchen/temperature' matches a subscriber filter 'home/+/temperature' because '+' matches 'kitchen'. However, 'home/livingroom/humidity' does not match 'home/+/temperature' because the last level differs. The '#' wildcard matches all subtopics under a prefix, such as 'home/#' matching any topic starting with 'home'. This design pattern helps organize and route IoT messages efficiently.