IoT Hub connection not restored when connection to the WIFI AP is lost and then recovered about esp-azure

[Patrik-Berglund]

@jitin17

The IoT Hub SDK will it self handle the re-connection. I have made a small update to the "esp-azure" to make it work.

I will prepare a pull-request with the changes needed.

[jitin17]

@Patrik-Berglund In case of AP connection loss, there is a need to re-connect to Azure IoT Hub.
And when there is an AP connection loss, we observe errno to be EHOSTUNREACH. So, we have added enhancement in iothub_client_sample_mqtt example to re-connect to Azure IoT Portal upon observing errno as EHOSTUNREACH. And we wait for WiFi STA state to be connected before connecting to Azure IoT Portal. Please refer to changes in iothub_client_sample_mqtt example to add corresponding changes in your example. Let us know whether this works or not.

[jitin17]

@Patrik-Berglund We have seen that azure-iot-sdk-c handles internet re-connection and connection to WiFi AP loss with the help of retry control handle. But there is a bug in azure-iot-sdk-c which causes crash; we have found the solution to it and will raise a PR soon. Thanks.

[Patrik-Berglund]

Great!

We switched to using the mbedtls and berkeley sockets based PAL provided by the IoT Hub C SDK instead. Required only minimal changes to their code.