Distributed MQTT IoT Network

A multi-device IoT system demonstrating real-time sensor-to-actuator control, device presence monitoring, and fault-tolerant messaging using the MQTT protocol.

System Overview

This project coordinates three Raspberry Pis and two laptops through a locally hosted MQTT broker.

• RasPi A → Publishes sensor data (LDR + potentiometer) with retain + last-will.
• RasPi C → Subscribes to sensor values, compares against thresholds, publishes LED control signals.
• RasPi B → Subscribes to device statuses and LED signals, drives three LEDs for visualization.
• Laptop 1 → Runs MQTT broker.
• Laptop 2 → Subscribes to all topics, logs messages with timestamps.

Features

• Distributed IoT architecture with multiple publishers and subscribers
• Online/offline detection using retained messages + last-will
• Real-time sensor threshold → actuator logic
• Centralized logging and duplicate message suppression

Architecture Diagram

flowchart LR
    subgraph Broker [Laptop 1 - MQTT Broker]
    end
    RasPiA -->|lightSensor/threshold| Broker
    RasPiC -->|LightStatus| Broker
    RasPiA -->|Status/RaspberryPiA| Broker
    RasPiC -->|Status/RaspberryPiC| Broker
    Broker --> RasPiB
    Broker --> Laptop2

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