MQTT with QoS levels in Raspberry Pi - Mini Project: Build & Apply

MQTT with QoS levels

📖 Scenario: You have a Raspberry Pi that collects temperature data. You want to send this data to a server using MQTT. MQTT allows you to choose how reliable the message delivery is by setting Quality of Service (QoS) levels.QoS 0 means the message is sent once with no confirmation. QoS 1 means the message is sent at least once, with confirmation. QoS 2 means the message is sent exactly once, with a more complex handshake.

🎯 Goal: Create a simple Python program on your Raspberry Pi that publishes a temperature reading to an MQTT broker using different QoS levels. You will set up the data, configure the QoS level, publish the message, and then print the result.

📋 What You'll Learn

Use the paho-mqtt Python library to connect to an MQTT broker.

Create a variable with a temperature reading.

Create a variable to set the QoS level (0, 1, or 2).

Publish the temperature message with the chosen QoS level.

Print a confirmation message showing the QoS level used.

💡 Why This Matters

🌍 Real World

MQTT is widely used in IoT devices like Raspberry Pi to send sensor data reliably to servers or cloud services.

💼 Career

Understanding MQTT and QoS levels is important for roles in IoT development, embedded systems, and network programming.

1

DATA SETUP: Create a temperature variable

Create a variable called temperature and set it to the float value 23.5 representing the temperature reading.

Raspberry Pi

# Create a variable called temperature and set it to 23.5
# Your code here

Need a hint?

Use a simple assignment like temperature = 23.5.

2

CONFIGURATION: Set the QoS level

Create a variable called qos_level and set it to the integer 1 to represent the MQTT QoS level.

Raspberry Pi

temperature = 23.5
# Create a variable called qos_level and set it to 1
# Your code here

Need a hint?

Set qos_level to 1 using simple assignment.

3

CORE LOGIC: Publish the temperature with QoS

Import the paho.mqtt.client module as mqtt. Create a client called client. Connect to the broker at "test.mosquitto.org" on port 1883. Publish the temperature to the topic "home/temperature" using the qos_level. Disconnect the client after publishing.

Raspberry Pi

temperature = 23.5
qos_level = 1
# Import paho.mqtt.client as mqtt
# Create client, connect to broker, publish temperature with qos_level, then disconnect
# Your code here

Need a hint?

Use client.publish(topic, message, qos=qos_level) to send the message.

4

OUTPUT: Print confirmation message

Write a print statement that outputs: "Published temperature 23.5 with QoS 1" using the variables temperature and qos_level inside an f-string.

Raspberry Pi

import paho.mqtt.client as mqtt

temperature = 23.5
qos_level = 1

client = mqtt.Client()
client.connect("test.mosquitto.org", 1883)
client.publish("home/temperature", str(temperature), qos=qos_level)
client.disconnect()
# Print confirmation message below
# Your code here

Need a hint?

Use print(f"Published temperature {temperature} with QoS {qos_level}").