MQTT (Message Queueing Telemetry Transport) is a lightweight messaging protocol for IoT devices that uses a publish-subscribe model for communication. It is designed to be efficient and low-overhead, making it ideal for use in resource-constrained environments such as those found on small devices like sensors and actuators.
For example, imagine a smart home system that uses MQTT to connect a temperature sensor to a thermostat. The sensor would "publish" temperature data to a topic (e.g. "home/temperature"), and the thermostat would "subscribe" to that topic to receive the data. The thermostat can then use the data to adjust the temperature of the house accordingly.
In this example, the temperature sensor and thermostat are two different clients that communicate with each other through a central broker (server) which is responsible for routing the messages between the clients.
What is an MQTT broker and what are the most popular MQTT brokers?
An MQTT broker is a server that acts as a central hub for MQTT clients to connect to. The broker is responsible for receiving messages from MQTT clients, determining which clients are subscribed to which topics, and forwarding the messages on to the appropriate clients.
There are many MQTT brokers available, both open-source and commercial. Some of the most popular open-source MQTT brokers include:
- Mosquitto: A widely-used open-source broker that is lightweight and easy to set up.
- HiveMQ: An enterprise-grade broker with a wide range of features and scalability.
- VerneMQ: A high-performance broker that is designed for large-scale and low-latency deployments.
- EMQ: An open-source broker with a web-based management interface and support for clustering.
There are also commercial MQTT brokers such as AWS IoT, Google IoT Core, Azure IoT Hub and IBM Watson IoT Platform, which offer more advanced features and support for enterprise use cases.