Publishing sensor data in IOT Protocols - Step-by-Step Execution

Process Flow - Publishing sensor data

Sensor reads data

↓

Format data as message

↓

Connect to broker/server

↓

Publish message to topic

↓

Broker receives and forwards

↓

Subscribers receive data

↓

Done

The sensor reads data, formats it, connects to a broker, publishes the message, and subscribers receive it.

Execution Sample

IOT Protocols

sensor_data = 25.3
message = f"temperature:{sensor_data}"
broker.connect()
broker.publish("home/sensor/temp", message)

This code reads a temperature, formats it, connects to the broker, and publishes the data.

Process Table

Step	Action	Data/Variable	Result/State Change	Output
1	Sensor reads data	sensor_data	sensor_data = 25.3
2	Format data as message	message	message = "temperature:25.3"
3	Connect to broker	broker.connection	broker.connection = True
4	Publish message	topic, message	Message sent to topic 'home/sensor/temp'
5	Broker forwards message	broker	Subscribers notified
6	Subscribers receive data	subscribers	Data received: 'temperature:25.3'
7	End		Publishing complete

💡 Publishing process completes after subscribers receive the data.

Status Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	After Step 4	Final
sensor_data	undefined	25.3	25.3	25.3	25.3	25.3
message	undefined	undefined	temperature:25.3	temperature:25.3	temperature:25.3	temperature:25.3
broker.connection	False	False	False	True	True	True

Key Moments - 3 Insights

Why do we format the sensor data into a message before publishing?

Because the broker and subscribers expect data in a specific message format, as shown in step 2 of the execution_table where sensor_data is converted to a string message.

What happens if the broker connection is not established before publishing?

Publishing will fail because the broker.connection variable must be True before sending messages, as seen in step 3 and 4 where connection is established before publishing.

How do subscribers get the sensor data after publishing?

The broker forwards the message to all subscribers subscribed to the topic, shown in steps 5 and 6 where subscribers receive the data after broker forwards it.

Visual Quiz - 3 Questions

Look at the execution_table, what is the value of 'message' after step 2?

A undefined

B "temperature:25.3"

C 25.3

D "sensor_data"

💡 Hint

Check the 'Data/Variable' column for step 2 in the execution_table.

At which step does the broker connection become True?

A Step 3

B Step 1

C Step 4

D Step 5

💡 Hint

Look at the 'Result/State Change' column for broker.connection in the execution_table.

If the sensor_data was 30.0 instead of 25.3, how would the message change after step 2?

A 30.0

B "temperature:25.3"

C "temperature:30.0"

D "sensor_data"

💡 Hint

Refer to the variable_tracker for 'message' after step 2 and how it depends on sensor_data.

Concept Snapshot

Publishing sensor data:
1. Sensor reads data (e.g., temperature).
2. Format data as a message string.
3. Connect to broker/server.
4. Publish message to a topic.
5. Broker forwards to subscribers.
6. Subscribers receive the data.

Full Transcript

Publishing sensor data involves reading the sensor value, formatting it into a message, connecting to a broker, publishing the message to a topic, and then subscribers receive the data. The process ensures data flows from sensor to interested receivers reliably.