MQTT
MQ Telemetry Transport (MQTT) is a lightweight messaging protocol that uses a publish-and-subscribe model that is intermediated by a broker. A publisher publishes messages under a given topic name to a broker. A subscriber to that topic at the broker will receive messages published under that topic name. For example, a publisher may be a temperature sensor in an agricultural field that sends a temperature reading (publishes the reading) to Broker Z at a particular time under a topic name of, say, MaizyWheatField-123A. An irrigation system computer that is subscribed to the topic MaizyWheatField-123A at Broker Z will receive the published temperature readings and can be programmed to switch on/off the irrigation system according to the latest published temperature.
MobileTogether supports MQTT by enabling MT solutions to join an MQTT network as a publisher, or as a subscriber, or as both. For example, in the diagram above, the MT solution named MT01 publishes messages to two topics (Topic-02 and Topic-XY), the MT solution named MT03 subscribes to Topic01, which is published by Publisher A, and the MT solution named MT04 subscribes to Topic-XY. Note that an MT solution can be both a publisher and a subscriber at the same time.
| Note: | An MT solution that is a subscriber can subscribe to topics published by both MobileTogether publishers as well as non-MobileTogether publishers. |
In the topics of this section, we describe the following:
•How to specify the solution actions to perform when the solution receives an MQTT message
•How to set up an MQTT service
•How to run a simulation to test the action tree that is executed when an MQTT message is received
MQTT specification and links
The documentation in this section explains how to set up your MobileTogether solution to publish, and subscribe to, MQTT messages and how to define actions to perform when an MQTT message is received. For more information about MQTT, see the following resources:
•the MQTT website
•the specification of MQTT Version 3.11, which is the version supported in MobileTogether