MQTT Broker with Optional TLS Support

This project implements an MQTT broker in Dart with support for optional SSL/TLS encryption. It is lightweight, customizable, and adheres to MQTT protocol specifications.

Features

• MQTT Protocol Support: Implements core MQTT protocol functionality.
• TLS/SSL Support: Provides secure connections using a self-signed or CA-signed certificate.
• Dynamic Event Handling: Customizable hooks for events like onConnect, onPublish, onSubscribe, etc.
• Retained Messages: Supports retained messages for topics.
• QoS Levels: Implements Quality of Service levels 0, 1, and 2.
• Last Will and Testament (LWT): Ensures client disconnection messages are handled.
• Wildcard Topics: Supports topic filters with + and # wildcards.

Future Features

The following features can be considered for future development:

• MQTT Version 5.0 Support:
  • User Properties: Allow custom metadata for MQTT messages.
  • Session Expiry: Handle session expiration intervals.
  • Reason Codes: Include reason codes in acknowledgments.
• Clustered Deployment:
  • Support for scaling the broker horizontally with multiple nodes.
  • Distributed session and topic management.
• Enhanced Authentication:
  • Support for username/password-based authentication.
  • Integration with OAuth2, JWT, or external authentication providers.
• WebSocket Support:
  • Allow MQTT over WebSocket connections for web-based clients.
• Message Persistence:
  • Store published messages in a database for durability.
  • Support replaying messages to new subscribers.
• Monitoring and Metrics:
  • Real-time monitoring of connected clients and topics.
  • Metrics for message throughput, latency, and resource usage.
• Advanced Access Control:
  • Topic-based access permissions for clients.
  • Integration with ACL (Access Control List) systems.
• HTTP API for Administration:
  • RESTful API to manage clients, topics, and broker settings.

Requirements

• Dart SDK (>=2.12)

Installation

1. Clone the repository:

   git clone https://github.com/mskayali/dart_mqtt_broker.git
   cd mqtt-broker-dart

2. Install dependencies:

   dart pub get

Usage

Starting the Broker

The broker can be run in either secure (TLS) or non-secure mode.

Insecure Mode

void main() {
  final broker = MQTTBroker(host: '0.0.0.0', port: 1883);
  broker.start();
}

Secure Mode

void main() {
  final broker = MQTTBroker(
    host: '0.0.0.0',
    port: 8883,
    certificatePath: 'path/to/certificate.pem',
    privateKeyPath: 'path/to/private.key',
  );
  broker.start();
}

Event Hooks

The broker provides event hooks for common MQTT actions:

void main() {
  final broker = MQTTBroker(port: 1883);

  // Register event handlers
  broker.events.onConnect((client) => print('Client connected: $client'));
  broker.events.onPublish((client, data) => print('Publish received: $data'));
  broker.events.onSubscribe((client, data) => print('Subscription: $data'));
  broker.events.onUnsubscribe((client, data) => print('Unsubscription: $data'));
  broker.events.onPing((client) => print('Ping received'));
  broker.events.onDisconnect((client) => print('Client disconnected: $client'));
  broker.events.onWill((client, topic, message) {
    print('Last Will from $client: $topic -> $message');
  });

  broker.start();
}

Certificate Setup

Generating a Self-Signed Certificate

1. Generate a private key:

   openssl genrsa -out private.key 2048

2. Generate a self-signed certificate:

   openssl req -new -x509 -key private.key -out certificate.pem -days 365

Using the Certificate

• Place certificate.pem and private.key in your project directory.
• Provide their paths when initializing the broker in secure mode.

Testing

Running Unit Tests

dart test

Connecting with an MQTT Client

Use any MQTT client to connect to the broker:

Insecure Connection

mosquitto_pub -h localhost -p 1883 -t test/topic -m "Hello World"

Secure Connection

mosquitto_pub --cafile certificate.pem -h localhost -p 8883 -t test/topic -m "Hello Secure World"

Folder Structure

├── handlers/          # Packet handlers (connect, publish, etc.)
├── models/            # Core models (Client, Topic, EventBroadcaster)
├── test/              # Unit tests
├── main.dart          # Example entry point
├── broker.dart        # Main broker implementation
└── README.md          # Project documentation

Contributing

Contributions are welcome! Please submit issues or pull requests via GitHub.

License

This project is licensed under the MIT License. See LICENSE for details.