Forum Discussion
IoT Hub Device twin returning connectionState = Disconnected, when it's actually connected
Hi!
You should have a look here: Device heartbeat
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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.
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Hope that helps!
Thanks
I don't care much about disconnects of less than a few minutes, I'm more concerted about disconnects that don't come back and get connected (ie 5 minutes or longer). Then I know there is some kind of issue. I guess I will just subscribe to a disconnect event and notify on that and not worry about connection events
A way you could implement a check on device connection would be to trigger a Function on the Device disconnected event that would invoke a direct method on the device with a timeout of 5 minutes. If the device comes back online in the 5 minutes, then the method will get answered. If not, you'll know the device has been disconnected for 5 minutes and can trigger the alert.
ahh....yes, was thinking I would have to ping all devices every 5 minutes, that makes a lot more sense.
Thank you for the suggestion...it seems to be the easiest and cleanest way to do that!
Actually it won't. The function is only triggered once when IoT Hub gets the Device disconnected event, tries the method call with 5 minutes timeout and if noone answers it sends a notification out that the device is disconnected. The Function doesn't loop.
The problem with that is it will send many messages (ie running every 5 minutes, 24x7) and would not be very cost effective from a hosting standpoint.