MQTT stands for Message Queuing Telemetry Transport. It works on top of the TCP/IP protocol. It is designed for connections where network bandwidth is limited. An MQTT system consists of clients communicating with a server, often called a "broker". When a publisher (such as a Retail Sensing people counter) has a new item of data to distribute, it sends a message with the data to the connected broker. The broker then distributes the information to any clients that have subscribed to that topic.