MQTT broker role in IOT Protocols - Mini Project: Build & Apply

Understanding the MQTT Broker Role

📖 Scenario: You are working on a smart home system where multiple devices communicate using MQTT. You need to understand how the MQTT broker manages message delivery between devices.

🎯 Goal: Build a simple simulation of an MQTT broker role using Python dictionaries and functions to show how messages are received from publishers and sent to subscribers.

📋 What You'll Learn

Create a dictionary to hold topics and their subscribers

Add a function to register subscribers to topics

Add a function to publish messages to a topic and deliver to subscribers

Print the messages delivered to each subscriber

💡 Why This Matters

🌍 Real World

MQTT brokers are central in IoT systems to route messages between devices like sensors, lights, and controllers.

💼 Career

Understanding MQTT broker roles helps in configuring and troubleshooting IoT networks and cloud messaging services.

1

Create the topics dictionary

Create a dictionary called topics with these exact keys: 'home/livingroom' and 'home/kitchen'. Each key should have an empty list as its value to hold subscribers.

IOT Protocols

# Create the topics dictionary with empty subscriber lists
# Your code here

Need a hint?

Think of topics as channels where devices subscribe to get messages.

2

Add subscriber registration function

Add a function called subscribe that takes topic and client as parameters and appends client to the list in topics[topic].

IOT Protocols

topics = {'home/livingroom': [], 'home/kitchen': []}

# Define subscribe(topic, client) to add client to topics[topic]
# Your code here

Need a hint?

This function lets a device say it wants messages from a topic.

3

Add publish function to send messages

Add a function called publish that takes topic and message as parameters. It should loop over each client in topics[topic] and print "Delivering '{message}' to {client}".

IOT Protocols

topics = {'home/livingroom': [], 'home/kitchen': []}

def subscribe(topic, client):
    topics[topic].append(client)

# Define publish(topic, message) to deliver message to all clients subscribed to topic
# Your code here

Need a hint?

This simulates the broker sending messages to all subscribers of a topic.

4

Subscribe clients and publish messages

Use subscribe to add 'device1' and 'device2' to 'home/livingroom', and 'device3' to 'home/kitchen'. Then call publish to send 'Lights on' to 'home/livingroom' and 'Temperature 22C' to 'home/kitchen'. This will print the delivery messages.

IOT Protocols

topics = {'home/livingroom': [], 'home/kitchen': []}

def subscribe(topic, client):
    topics[topic].append(client)

def publish(topic, message):
    for client in topics[topic]:
        print(f"Delivering '{message}' to {client}")

# Subscribe devices and publish messages
# Your code here

Need a hint?

Devices get messages only for topics they subscribed to.