MQTT protocol (Message Queuing Telemetry Transport) is a common language through which sensors, actuators and machines can communicate with each other. It is a lightweight publish and subscribe system. The protocol was developed as a simple system to transfer data with a low bandwidth. Thanks to these properties, MQTT is very suitable for use within Internet of Things applications. MQTT is used in various industries such as automotive, manufacturing, telecommunications, oil and gas. MQTT uses the following basic concepts: Publish/Subscribe, Messages, Topics and Broker.
Publish and subscribe principle
First of all, the Publish and Subscribe principle. A device can publish a message on a topic. It is also possible to subscribe to a so-called topic, whereby we indicate that we want to receive the message of this topic.
MQTT and Topics
A topic is the way in which it is indicated how a message is published, or how it is indicated which messages should be received. Topics are displayed as a string separated by a slash. Each slash indicates a level. The broker is ultimately responsible for receiving all messages. When a device publishes a message, it will go to the broker.