MQTT (MQ Telemetry Transport or Message Queue Telemetry Transport) is an ISO standard (ISO/IEC PRF 20922) publish-subscribe-based messaging protocol. It works on top of the TCP/IP protocol. It is designed for connections with remote locations where a "small code footprint" is required or the network bandwidth is limited. The publish-subscribe messaging pattern requires a message broker.
The specification does not specify the meaning of "small code footprint" or the meaning of "limited network bandwidth". Thus, the protocol's availability for use depends on the context. In 2013, IBM submitted MQTT v3.1 to the OASIS specification body with a charter that ensured only minor changes to the specification could be accepted. MQTT-SN  is a variation of the main protocol aimed at embedded devices on non-TCP/IP networks, such as ZigBee.
Alternative protocols include the Advanced Message Queuing Protocol (AMQP), Streaming Text Oriented Messaging Protocol (STOMP) the IETF Constrained Application Protocol, XMPP , OPC UA and Web Application Messaging Protocol (WAMP).
Waits for a connection to be established with the server and creates a link between the nodes.
Waits for the MQTT client to finish any work it must do, and for the TCP/IP session to disconnect.
Returns immediately to the application thread after passing the request to the MQTT client.
Quality of Service (QOS)Edit
Quality of service refers to traffic prioritization and resource reservation control mechanisms rather than the achieved service quality. Quality of service is the ability to provide different priority to different applications, users, or data flows, or to guarantee a certain level of performance to a data flow.
There are several projects that implement MQTT. Examples are:
- Facebook Messenger. Facebook has used aspects of MQTT in Facebook Messenger for online chat. However, it is unclear how much of MQTT is used or for what.
- IECC Scalable, DeltaRail's latest version of their IECC Signaling Control System uses MQTT for communications within the various parts of the system and other components of the signaling system. It provides the underlying communications framework for a system that is compliant with the CENELEC standards for safety-critical communications.
- The EVRYTHNG IoT platform uses MQTT as an M2M protocol for millions of connected products.
- Amazon Web Services announced Amazon IoT based on MQTT in 2015.
- The Open Geospatial Consortium SensorThings API standard specification has a MQTT extension in the standard as an additional message protocol binding. It was demonstrated in a US Department of Homeland Security IoT Pilot.
- The OpenStack Upstream Infrastructure's services are connected by an MQTT unified message bus with Mosquitto as the MQTT broker.
- Adafruit launched a free MQTT cloud service for IoT experimenters and learners called Adafruit IO in 2015.
- Microsoft Azure IoT Hub uses MQTT as its main protocol for telemetry messages.
- XIM, Inc. launched an MQTT client called MQTT Buddy in 2017. It's a MQTT app for Android and iOS, but not F-Droid, users available in English, Russian and Chinese languages.
- Node-RED supports MQTT nodes as of version 0.14, in order to properly configure TLS connections.
- Open-source software home automation platform Home Assistant is MQTT enabled and offers four options for MQTT brokers.
- Pimatic home automation framework for Raspberry Pi and based on Node.js offers MQTT plugin providing full support for MQTT protocol.
- McAfee OpenDXL is based on MQTT with enhancements to the messaging brokers themselves so that they can intrinsically understand the DXL message format in support of advanced features such as services, request/response (point-to-point) messaging, service fail over, and service zones.
- "MQTT 3.1.1 specification". OASIS. December 10, 2015. Retrieved April 25, 2017.
- "ISO/IEC 20922:2016 Information technology -- Message Queuing Telemetry Transport (MQTT) v3.1.1". iso.org. International Organization for Standardization. June 15, 2016.
- "10th birthday party". MQTT.org. July 2009. Retrieved April 25, 2015.
- "OASIS Message Queuing Telemetry Transport (MQTT) Technical Committee". OASIS. Retrieved May 9, 2014.
- Stanford-Clark, Andy; Hong Linh Truong (November 14, 2013). "MQTT For Sensor Networks (MQTT-SN) Protocol Specification Version 1.2" (PDF). mqtt.org. MQTT. p. 27. Retrieved May 9, 2014.
- "IBM WebSphere MQ". IBM. Retrieved November 18, 2013.
- Piper, Andy (February 19, 2013). "Choosing Your Messaging Protocol: AMQP, MQTT, or STOMP". blogs.vmware.com. VMware Blogs. p. 1. Retrieved October 23, 2013.
- Shelby, Zach; Hartke, Klaus; Bormann, Carsten (June 26, 2014). "Constrained Application Protocol (CoAP) RFC 7252". tools.ietf.org. IETF. p. 1. Retrieved November 15, 2015.
- XMPP community (November 1, 2013). "InternetOfThings". wiki.xmpp.org. XMPP wiki. p. 1. Retrieved May 9, 2014.
- Baker, Fred; Meyer, David (June 21, 2011). "Internet Protocols for the Smart Grid RFC 6272". datatracker.ietf.org. IETF. p. 1. Retrieved May 9, 2014.
- "Microsoft introduces new open-source cross-platform OPC UA support for the industrial Internet of Things - Internet of Things". Internet of Things. 2016-06-23. Retrieved 2017-10-13.
- Zhang, Lucy (August 12, 2011). "Building Facebook Messenger". facebook.com/Engineering. Facebook. p. 1. Retrieved October 15, 2015.
By maintaining an MQTT connection and routing messages through our chat pipeline, we were able to often achieve phone-to-phone delivery in the hundreds of milliseconds, rather than multiple seconds.
- Wood, Daren; Robson, Dave (August 13, 2012). "Message broker technology for flexible signalling control" (PDF). irse.org. IRSE. p. 7. Retrieved March 31, 2014.
- Barr, Jeff (October 8, 2015). "AWS IoT - Cloud Services for Connected Devices". aws.amazon.com. Amazon Web Services. p. 1. Retrieved October 21, 2015.
- "AWS IoT". aws.amazon.com/iot. Amazon Web Services. p. 1. Retrieved July 1, 2017.
- Brothers, Reginald (January 25, 2016). "S&T's Internet of Things Pilot Demonstrates 'State of the Practical'". dhs.gov. p. 1. Retrieved March 31, 2016.
- "OpenStack Firehose - The unified message bus for Infra services". docs.openstack.org. OpenStack Infastructure Team. p. 1. Retrieved August 30, 2016.
- "Coming Soon: Adafruit IO". blog.adafruit.com. Adafruit Industries. September 16, 2014. p. 1. Retrieved March 29, 2017.
- "The Internet of Things for Everyone". io.adafruit.com. Adafruit. p. 1. Retrieved July 1, 2017.
- Dotchkoff, Konstantin; Betts, Dominic; Kshirsagar, Dhanashri; mastermanu; Damaggio, Elio (March 1, 2017). "Understanding Microsoft Azure MQTT Support". docs.microsoft.com. Microsoft. p. 1. Retrieved March 29, 2017.
- "The story of MQTT Buddy begins!". mqtt.ximxim.com. XIM, Inc. February 24, 2017. p. 1. Retrieved July 1, 2017.
- "MQTT Buddy". mqtt.ximxim.com. XIM, Inc. Retrieved July 1, 2017.
- Community staff writer (June 14, 2016). "Version 0.14 released". nodered.org/blog. Node-RED. Retrieved July 6, 2016.
MQTT with TLS support
- Home Assistant Community (August 7, 2015). "MQTT". home-assistant.io. Home Assistant Community. Retrieved August 4, 2017.
- Home Assistant Community (August 7, 2015). "MQTT Brokers". home-assistant.io. Home Assistant Community. Retrieved August 4, 2017.
The MQTT component needs you to run an MQTT broker for Home Assistant to connect to. There are four options, each with various degrees of ease of setup and privacy.
- Kail, Marek (October 16, 2016). "pimatic-mqtt". pimatic.org. Oliver Schneider. Retrieved August 11, 2017.
- "What protocol does OpenDXL use? - OpenDXL". OpenDXL. Retrieved 2017-10-13.
- McDonald, Ted. "Architecture Guide McAfee Data Exchange Layer (DXL)" (PDF).