MQ Telemetry Transport
MQ Telemetry Transport (MQTT)  is a publish-subscribe based "light weight" messaging protocol for use on top of the TCP/IP protocol. It is designed for connections with remote locations where a "small code footprint" is required and/or network bandwidth is limited. The Publish-Subscribe messaging pattern requires a message broker. The broker is responsible for distributing messages to interested clients based on the topic of a message. The protocol was invented by Andy Stanford-Clark of IBM, and Arlen Nipper of Cirrus Link Solutions.
The specification does not specify the meaning of "small code foot print" or the meaning of "limited network bandwidth". Thus the protocol's availability for use will depend on the specific context. In 2013 IBM submitted MQTT v 3.1 to the OASIS specification body with a charter that ensured only minor changes to the specification could be accepted. MQTT-S  is a variation of the main protocol aimed at embedded devices on non-TCP/IP networks, such as ZigBee.
Historically, the 'MQ' in 'MQTT' came from IBM's MQ message queuing product line. However, there is no queuing in MQTT. Similarly, although the term Telemetry is used in its title, the protocol is not widely used in the sphere of Telemetry.
Real world applications
In the real world, there are a number of projects that implement MQTT. Some of these are:
- Facebook Messenger iOS iPhone and iPad, Android, and Windows apps. The recent revamped release of Facebook Mobile also makes use of MQTT for six different functions including status (presence services), bookmark sync. Facebook stated that they adopted MQTT to have faster phone to phone messaging while using less battery and bandwidth. It is unclear how much of MQTT is utilised and moreover it is to be noted that this is a phone application not a sensor application.
There are no references or independent sources for the following:
- St Jude Medical uses MQTT with its heart pacemakers to send cardio and pacemaker data for their clinicians remotely monitoring at home patients. This is done to provide the patients a better quality of life and reduce the amount of patient travel for check-ups.
- Real-time monitoring and control of 17,000 km of petroleum pipeline via 30,000 sensors and controllers connected by MQTT over satellite and terrestrial networks.
- Say It, Sign It: Real-time avatar rendering of British Sign Language
- Location Aware Messaging for Accessibility: Making information accessible
- Smart Lab: Monitoring experiments at the University of Southampton’s chemistry lab
- FloodNet: Monitoring river levels and environmental information to provide early warning of flooding
- MQTT 3.1 specification
- MQTT-S v1.2 specification
- IBM WebSphere MQ accessdate=2013-11-18
- Choosing Your Messaging Protocol: AMQP, MQTT, or STOMP | VMware vFabric Blog - VMware Blogs. Blogs.vmware.com (2013-02-19). Retrieved on 2013-10-23.
- MQTT.org Broker List Exhaustive list of available MQTT brokers
- MQTT Broker Feature Comparison Feature comparison of the most popular MQTT brokers.