Few devices under Azure IoT hub are showing as Disconnected

Question

Hi,

We have created 02 IoT hub instances to collect data from On-Premise servers to Azure Datalake. under each instance there are 7-8 devices created, all were running well from last couple oy years, recently from 11th Feb onwards the dataflow stopped for most of the devices in both instances.

During trouble shooting, i found an error code as 400027 in the Azure IoT hub logs, which is saying that:
400027 Connection forcefully closed on new connection (referred from the documentation https://learn.microsoft.com/en-us/azure/iot-hub/troubleshoot-error-codes#400027-connection-forcefully-closed-on-new-connection)

The diagnostics says that
"This error occurs when another client creates a new connection to IoT Hub using the same identity, so IoT Hub closes the previous connection. IoT Hub doesn't allow more than one client to connect using the same identity.

To resolve this error, ensure that each client connects to IoT Hub using its own identity."

I have cross verified the connection strings of each device at Azure side and all are seems to be unique.

Can i get few more tips to resolve this issue, i have not worked much with the trouble shooting since we do not got frequent errors in past (earlier there was similar error which was resolved by MS support team and the root cause was found as the Gateway version upgrade of IoT hub device).

Kindly help to resolve this and if you need more information, do let me know.

Regards

Satish

Answer 1

Hello @Satish Kumar,

welcome to this moderated Azure community forum.

On 10 February 2025 there was an outage on Azure around 19:00 UTC. This included the West-Europe region.

Perhaps your devices encountered this issue too?

Can you reset the devices that are not connected yet?

If not, create an Azure support ticket so the support team can take a look at the backend.

Notice that the same 400027 error can also related to failing device-to-cloud twin operations (such as read or patch reported properties) or direct method invocations.

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