IoT Agent - HTTP & MQTT command (southbound)

asked 2019-12-03 12:06:57 +0100

GuyD
11 ●6 ●8 ●9

Hello,

To me it's not clear if a device needs to take the initiative (pull) to get southbound/commands from the IoT Agent (http transport) or the IoT Agent takes the initiative (push) to the device?

For MQTT I suppose the IoT agent subscribes to the MQTT (Mosquitto) broker and subscribes and/or publishes to the MQTT broker?

Thanks for the clarification.

Guy

answered 2020-06-22 15:50:49 +0100

Jason Fox
31 ●1 ●4

The reason that this remains unclear is that both options are possible.

an active attribute ( that is configured as part of the attributes array) must actively send measures to the agent
a lazy attribute ( that is configured as part of the lazy array) is requested by the IoT Agent whenever the context broker receives a request for the device.

Taking the HTTP transport as an example, the IoT Agent listens to the context broker on the north port and a "well-known" location on the southport so devices can send info to it. In the case of a lazy attribute the IoT Agent knows where to forward the request based on the resource defined by the configuration.

Taking the MQTT transport as an example, the IoT Agent listens to the context broker on the north port and subscribes to MQTT topics for each of the devices. In the case of a lazy attribute the IoT Agent publishes a topic for an update and polls and waits for the response before passing back to the context broker.

Active attributes are by far the commonest way to provision devices.