How MQTT Works

What is MQTT, and how does it work?

MQTT was developed in the late 90s by IBM. It was used in specific industries that required lightweight communication. But its widespread adoption occurred with the rise of the Internet of Things (IoT) landscape. MQTT (Message Queuing Telemetry Transport) is a lightweight messaging protocol optimized for high-latency or unreliable networks. Its minimal bandwidth and resource consumption, along with support for real-time data transmission, among other qualities, have made it ideal for IoT environments. From simple sensors to complex industrial machines, MQTT facilitates efficient data exchange, even in unreliable network conditions. MQTT operates on top of TCP/IP. It’s focused on simple, efficient, and reliable message exchange.

Below are the core concepts of MQTT:

  • Broker — this central hub ensures that messages reach their intended destinations.

  • Client — any MQTT-enabled device capable of publishing and receiving messages.

  • Topic — a defined category for publishing and subscribing to messages that makes communication organized.

  • Quality of Service — categorizes the guarantee level for message delivery based on its urgency.

  • Message — the actual data being transmitted between clients and the broker.

  • Session — the state maintained between a client and a broker, including subscriptions and undelivered messages.

The MQTT communication flow is quite straightforward:

  1. Clients connect to the MQTT broker and subscribe to topics of interest.

  2. When a client publishes a message to a topic, the broker receives and processes it.

  3. The broker then forwards the message to every client who has subscribed to that topic.

This streamlined process, together with the protocol’s lightweight nature, makes MQTT ideal for IoT scenarios with limited connectivity or stringent power constraints. MQTT ensures efficient data transmission and offers reliable message delivery across various network conditions. This reliability is complemented by support for multiple QoS levels to meet diverse requirements. These features enable real-time monitoring and control and improve the scalability and responsiveness of IoT systems. With its reliable, scalable, and resource-conscious messaging solution, MQTT forms the backbone of IoT communication.