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MQTT
MQTT is a lightweight, publish–subscribe, machine-to-machine network protocol for message queue/message queuing service. It is designed for connections with remote locations that have devices with resource constraints or limited network bandwidth, such as in the Internet of things (IoT). It must run over a transport protocol that provides ordered, lossless, bi-directional connections—typically, TCP/IP. It is an open OASIS standard and an ISO recommendation (ISO/IEC 20922).
Andy Stanford-Clark (IBM) and Arlen Nipper (then working for Eurotech, Inc.) authored the first version of the protocol in 1999. It was used to monitor oil pipelines within the SCADA industrial control system. The goal was to have a protocol that is bandwidth-efficient, lightweight and uses little battery power, because the devices were connected via satellite link, which was extremely expensive at that time.
Historically, the "MQ" in "MQTT" came from the IBM MQ (then "MQSeries") product line, where it stands for "Message Queue". However, the protocol provides publish-and-subscribe messaging (no queues, in spite of the name). In the specification opened by IBM, as version 3.1, the protocol was referred to as "MQ Telemetry Transport". Subsequent versions released by OASIS strictly refer to the protocol as just "MQTT", although the technical committee itself is named "OASIS Message Queuing Telemetry Transport Technical Committee". Since 2013, "MQTT" does not stand for anything.
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. After taking over maintenance of the standard from IBM, OASIS released version 3.1.1 on October 29, 2014. A more substantial upgrade to MQTT version 5, adding several new features, was released on March 7, 2019.
MQTT-SN (MQTT for Sensor Networks) is a variation of the main protocol aimed at battery-powered embedded devices on non-TCP/IP networks, such as Zigbee.
The MQTT protocol defines two types of network entities: a message broker and a number of clients. An MQTT broker is a server that receives messages from publishing clients and then routes the messages to the appropriate destination clients. An MQTT client is any device (from a microcontroller up to a full-fledged server) that runs an MQTT library and connects to an MQTT broker over a network.
Information is organized in a hierarchy of topics. When a publisher has a new item of data to distribute, it sends a control message with the data to the connected broker. The broker then distributes the information to any clients that have subscribed to that topic. The publisher does not need to have any data on the number or locations of subscribers; and subscribers, in turn, do not have to be configured with any data about the publishers.
If a broker receives a message on a topic for which there are no current subscribers, the broker discards the message unless the publisher of the message designated the message as a retained message. A retained message is a normal MQTT message with the retained flag set to true. The broker stores the last retained message and the corresponding quality of service (QoS) for the selected topic. Each client that subscribes to a topic pattern that matches the topic of the retained message receives the retained message immediately after they subscribe. The broker stores only one retained message per topic. This allows new subscribers to a topic to receive the most current value rather than waiting for the next update from a publisher.
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MQTT AI simulator
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MQTT
MQTT is a lightweight, publish–subscribe, machine-to-machine network protocol for message queue/message queuing service. It is designed for connections with remote locations that have devices with resource constraints or limited network bandwidth, such as in the Internet of things (IoT). It must run over a transport protocol that provides ordered, lossless, bi-directional connections—typically, TCP/IP. It is an open OASIS standard and an ISO recommendation (ISO/IEC 20922).
Andy Stanford-Clark (IBM) and Arlen Nipper (then working for Eurotech, Inc.) authored the first version of the protocol in 1999. It was used to monitor oil pipelines within the SCADA industrial control system. The goal was to have a protocol that is bandwidth-efficient, lightweight and uses little battery power, because the devices were connected via satellite link, which was extremely expensive at that time.
Historically, the "MQ" in "MQTT" came from the IBM MQ (then "MQSeries") product line, where it stands for "Message Queue". However, the protocol provides publish-and-subscribe messaging (no queues, in spite of the name). In the specification opened by IBM, as version 3.1, the protocol was referred to as "MQ Telemetry Transport". Subsequent versions released by OASIS strictly refer to the protocol as just "MQTT", although the technical committee itself is named "OASIS Message Queuing Telemetry Transport Technical Committee". Since 2013, "MQTT" does not stand for anything.
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. After taking over maintenance of the standard from IBM, OASIS released version 3.1.1 on October 29, 2014. A more substantial upgrade to MQTT version 5, adding several new features, was released on March 7, 2019.
MQTT-SN (MQTT for Sensor Networks) is a variation of the main protocol aimed at battery-powered embedded devices on non-TCP/IP networks, such as Zigbee.
The MQTT protocol defines two types of network entities: a message broker and a number of clients. An MQTT broker is a server that receives messages from publishing clients and then routes the messages to the appropriate destination clients. An MQTT client is any device (from a microcontroller up to a full-fledged server) that runs an MQTT library and connects to an MQTT broker over a network.
Information is organized in a hierarchy of topics. When a publisher has a new item of data to distribute, it sends a control message with the data to the connected broker. The broker then distributes the information to any clients that have subscribed to that topic. The publisher does not need to have any data on the number or locations of subscribers; and subscribers, in turn, do not have to be configured with any data about the publishers.
If a broker receives a message on a topic for which there are no current subscribers, the broker discards the message unless the publisher of the message designated the message as a retained message. A retained message is a normal MQTT message with the retained flag set to true. The broker stores the last retained message and the corresponding quality of service (QoS) for the selected topic. Each client that subscribes to a topic pattern that matches the topic of the retained message receives the retained message immediately after they subscribe. The broker stores only one retained message per topic. This allows new subscribers to a topic to receive the most current value rather than waiting for the next update from a publisher.