Raspberry Pi MQTT Gateway

Overview

This Raspberry Pi script (Pi_Script.py) acts as a secure MQTT gateway, bridging NodeMCU (ESP8266) sensor devices and a cloud web application (Azure IoT Hub). It enables secure bidirectional communication, handling device identity, message forwarding, and local broker management.

Features

• Dual MQTT Clients: Maintains connections to both a local Mosquitto MQTT broker (for ESP devices) and Azure IoT Hub (cloud).
• Certificate-based TLS Security: Uses client and CA certificates for secure cloud connections.
• Automatic Broker Management: Installs and starts the local Mosquitto broker if needed.
• Warehouse ID Management: Loads, requests, and persists a unique warehouse ID from the cloud for identification.
• ESP Device Onboarding: Forwards ESP MAC address to the cloud for cell assignment; relays assigned cell IDs back to ESPs.
• Bidirectional Data Flow:
  • Forwards ESP sensor/consumption data from local broker to the cloud.
  • Forwards web control and mode commands from the cloud to ESP devices.
• Robustness: Handles reconnection, signal-based shutdown, and cleans up stale requests.
• Configurable via environment (cert paths, IDs).

Requirements

• Python 3.x
• paho-mqtt, netifaces
• Local Mosquitto MQTT broker (auto-installed if missing)
• Certificates for Azure IoT Hub in /home/pi/pi/certs/

How It Works

1. Start & Setup:
   • Installs and starts Mosquitto if not present.
   • Verifies required certificates, loads warehouse ID (or requests one).
2. MQTT Connections:
   • Connects securely to Azure IoT Hub and locally to Mosquitto.
3. ESP Communication:
   • Listens for ESP ID requests and sensor data locally.
   • Forwards IDs and data to the cloud.
   • Relays web commands/modes from cloud to ESPs.
4. Shutdown:
   • Handles graceful shutdown on SIGINT/SIGTERM.

MQTT Topics

Cloud (Azure IoT Hub)

Topic	Direction	Description
wh/pi/id/request	Out	Request warehouse ID for Pi (by MAC)
wh/pi/<MAC>/id/response	In	Receives warehouse ID assignment
wh/esp/id/request	Out	Request ESP cell ID assignment
wh/<WAREHOUSE_ID>/esp/id/response	In	Receives assigned ESP cell ID
wh/<WAREHOUSE_ID>/esp/data	Out	ESP sensor data forwarded to cloud
wh/<WAREHOUSE_ID>/esp/consumption	Out	ESP consumption data forwarded to cloud
wh/<WAREHOUSE_ID>/esp/command	In	Control commands from web app to ESPs
wh/<WAREHOUSE_ID>/esp/mode/change	In	Mode change commands from web app to ESPs

Local (Mosquitto, ESP Devices)

Topic	Direction	Description
esp/id/request	In	ESP requests cell ID (by MAC)
esp/<MAC>/id/response	Out	Assigned cell ID sent to ESP
wh/esp/data	In	Sensor data from ESP
wh/esp/consumption	In	Consumption data from ESP
esp/commands	Out	Control commands relayed to ESPs
esp/mode/change	Out	Mode change relayed to ESPs

Setup

1. Place certificates in /home/pi/pi/certs/.
2. Install Python dependencies:

   pip install paho-mqtt netifaces

3. Run the script:

   python3 Pi_Script.py

   The script will auto-install Mosquitto if needed.

File Locations

• Script: Pi_Script.py
• Warehouse ID file: /home/pi/warehouse_id.txt
• Certificates: /home/pi/pi/certs/

License

MIT