MQTT (Message Queue Telemetry Transport) is a lightweight Machine to Machine (M2M) communication protocol that is used in Industry 4.0 and IoT applications environments.
It is an open standard (ISO / IEC PRF 20922) and it is based on the publication-subscription pattern. It works on the top of the TCP/IP stack. Its main objective is to exchange messages between clients and a server (Agent-Broker). Clients can decide for themselves if a message is important to them, depending on the topics to which they have subscribed.