dotnet/MQTTnet

Features

• Dual-Role Libraries - A full-featured MQTT library for .NET that supports both client and broker roles with message routing and session management.
• MQTT Clients - Sending and receiving messages to an MQTT broker with topic-based publish/subscribe, including automatic reconnection.
• MQTT Broker Connections - Provides TCP connection establishment and protocol version negotiation for MQTT broker communication.
• Resilient Connections - Maintaining reliable MQTT communication with automatic reconnection and message queueing to handle network interruptions.
• MQTT Message Brokers - Starts a server that listens for TCP connections, routes messages, manages client sessions, subscriptions, retained messages, and supports mixed protocol versions.
• Access Control Modules - Enforcing authentication and authorization on MQTT client connections and subscriptions to secure the messaging system.
• Access-Controlled Brokers - Hosts a broker that validates client credentials, enforces subscription rules, and stores retained messages for topic-based publish-subscribe.
• Non-Blocking TCP Servers - Manages network I/O with non-blocking sockets to handle thousands of concurrent connections without blocking threads.
• MQTT Message Handlers - Processes incoming MQTT messages asynchronously via callbacks for custom application logic.
• Publishers - Publishes messages to MQTT topics with configurable quality-of-service levels.
• Topic Subscribers - Subscribes to MQTT topics with support for wildcards and configurable quality-of-service.
• QoS Retransmission Engines - Guarantees exactly-once and at-least-once delivery by tracking packet IDs and retrying with flow control.
• Messaging Session Persistence - Stores client subscriptions and missed messages across restarts by serializing session data to a configurable storage backend.
• Transport Wrappers - Wraps raw TCP streams with encryption using configurable certificates and cipher suites for secure communication.
• MQTT TLS Encryption - Encrypting MQTT traffic over TLS to protect data in transit between clients and the broker.
• Broker-Initiated Publications - Injects a message directly from the broker into the topic tree, as if a client published it.
• QoS-Guaranteed Reconnections - Reconnects and resends messages with correct QoS to maintain reliable communication with the broker.
• QoS-Preserving Reconnections - Automatically reconnects and retransmits messages with correct quality-of-service to maintain reliable communication with the broker.
• MQTT Message Acknowledgements - Sends detailed acknowledgements with reason codes and user properties for received MQTT messages.
• MQTT Version Detectors - Detects the MQTT version in the CONNECT packet and adapts packet parsing and feature support accordingly.
• Message Interceptors - Routes every published message through user-defined interceptors before delivery to subscribers or retained message store.
• MQTT Credential Validators - Validates client credentials during MQTT connection handshake and rejects unauthorized clients.
• Client Credential Validators - Validates client credentials through configurable handlers that can reject connections with custom reason codes.
• MQTT Communication - High-performance library for MQTT clients and brokers.

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