Eclipse Mosquitto

Eclipse Mosquitto is an open-source message broker that implements the MQTT protocol (MQTT 5.0, 3.1.1, and 3.1). It is designed to be lightweight and efficient, making it suitable for IoT-style publish/subscribe messaging from small devices to full servers.

Key Features

• MQTT broker with support for MQTT v5.0, v3.1.1, and v3.1
• TLS support for encrypted client connections
• Authentication options including username/password and pluggable security extensions
• Access control via ACLs to restrict topic publishing and subscribing
• WebSockets support for MQTT clients in web environments (optional build feature)
• Includes client utilities (mosquitto_pub, mosquitto_sub) and C/C++ client libraries

Use Cases

• IoT messaging backbone for sensors, gateways, and embedded devices using pub/sub
• Smart home and industrial telemetry aggregation and command distribution
• Lightweight MQTT broker for development, testing, and internal messaging systems

Limitations and Considerations

• Advanced enterprise features like clustering and high availability are not part of the core open-source broker
• Some capabilities (for example, WebSockets or SRV lookups) may require optional build-time dependencies

Mosquitto is a solid choice when you need a small, fast, standards-compliant MQTT broker with strong protocol support and common security mechanisms. It scales from simple local testing to production deployments where reliable MQTT message routing is required.