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‘+’ sign means to subscribe to any topic in this level.To accomplish this wildcards (+ and #) are used. The subscription can be done to a certain topic or “pattern”. This can be used to organize data in a handy way.Įach device want to get data on a certain topic, must “subscribe” to it by informing the broker (server). The topics can be think of like a tag for each message, and can be in the form of one level or multi-levels (tree) each level separated by a slash (/) (.i.e: rooms/room1/sensors/temp ).

The publish/subscribe model is quite different from the request/response model in HTTP, and this allows for one-to-many message transfer. There is no direct connection between the publisher and subscriber, simply the subscriber tells the broker (server) which topics it interested in, and the broker handles sending a message with data for the requested topic/s to all subscribers.

The subscriber is the device which listens for topic/s.

These messages are labeled with a ‘topic’ name.

The publisher is the device which sends messages (publish) to the server.

The broker is the server responsible to manage the network of clients which are a mix of publishers and subscribers.

The MQTT model includes 3 main blocks: broker, publisher and subscriber.

It’s specially designed for IoT context with the limited resource environment in terms of power, bandwidth and footprint. It is light weight, open, simple, and designed so as to be easy to implement.” according to the official definition. MQTT or Message Queuing Telemetry Transport is “a Client Server publish/subscribe messaging transport protocol.