Device connection event for Azure Iothub

Question

The use case is to receive device connected event as soon as the device is connected to the iothub.

There is a device connected/disconnected event that can be captured and routed to eventhub/servicebus/eventgrid, but, this event isn’t triggered in Amqp if the message is sent by .net program i.e it is inconsistent.

Is there any mechanism available to get the recent device connected event in Iothub! Or heartbeat pattern is the only mechanism available or is most efficient way?

Answer 1

Your understanding is correct. Suggestion is to use the Device heartbeat pattern.

The IoT Hub identity registry contains a field called connectionState. Only use the connectionState field during development and debugging. IoT solutions should not query the field at run time. For example, do not query the connectionState field to check if a device is connected before you send a cloud-to-device message or an SMS. We recommend subscribing to the device disconnected event on Event Grid to get alerts and monitor the device connection state. Use this tutorial to learn how to integrate Device Connected and Device Disconnected events from IoT Hub in your IoT solution.

If your IoT solution needs to know if a device is connected, you can implement the heartbeat pattern. In the heartbeat pattern, the device sends device-to-cloud messages at least once every fixed amount of time (for example, at least once every hour). Therefore, even if a device does not have any data to send, it still sends an empty device-to-cloud message (usually with a property that identifies it as a heartbeat). On the service side, the solution maintains a map with the last heartbeat received for each device. If the solution does not receive a heartbeat message within the expected time from the device, it assumes that there is a problem with the device.