Usually, end devices have a limited memory and CPU power, running on batteries, so connecting them with servers requires a light protocol. Enter MQTT, which was invented in 1999 by Andy Stanford-Clark from IBM and Arlen Nipper from Arcom, a SCADA protocol design initially for battery operated devices to supervise oil pipelines. Later in 2010, IBM released it as a royalty-free protocol. In 2014, OASIS announced that the MQTT v.3.1.1 had become an OASIS standard and a lot of MQTT clients were developed for all programming languages.

The characteristics of MQTT are listed as follows:

• Data agnostic: MQTT can transport all kind of data, from sensor data to images or over the air updates
• Lightweight and bandwidth efficient: Smallest frame is only 2 bytes long
• Provide QoS: Three Quality of Service (QoS) levels
• Runs on top of the TCP/IP stack
• Simple to develop: Clients exist for all operating systems and programming languages
• Central broker: Can connect different devices without having to worry about compatibility
• Session awareness: Provides an identity-based approach for subscriptions
• Flexible subscription topics