Short answer
MQTT is a lightweight messaging protocol designed for devices with limited resources and unreliable connections. Devices publish messages to topics, and other devices or servers subscribe to them — for example, a sensor publishes the temperature and the system receives it immediately. It is one of the most widely used IoT protocols.
How MQTT works
- Broker — the server that all messages pass through.
- Publisher — a device that sends a message to a topic, for example “warehouse/1/temperature”.
- Subscriber — a system or device that listens to the topic and receives the messages.
Devices don’t need to know about each other — they communicate through the broker.
Why IoT solutions choose MQTT
- Small data volumes and low power consumption.
- Works even with an unreliable connection.
- Delivery guarantee levels (QoS).
- Commands can be sent back to the devices.
MQTT and HTTP
HTTP works well when a device rarely sends data or talks to an ordinary web API. MQTT is better when there are many devices, data flows often or you need real-time commands. We use both in our projects — for example, in the car wash and Barspector solutions.