MQTT Events to Azure IoT Hub

[FLSandberg]

I am experiencing an issue slightly similar to that described in https://github.com/orgs/AxisCommunications/discussions/734 , but for a different product and for sending telemetry to an Azure IoT Hub. I have the following setup:
AXIS P1465-LE-3 , OS version 11.11.78 , with AXIS License Plate Verifier, version 2.11.9 .
I was able to get through the guide at https://developer.axis.com/analytics/how-to-guides/send-telemetry-to-azure-iot-hub , after changing the server certificate to DigiCert Global root G2, and I am able to connect the device via MQTT.
However, any attempt to send useful telemetry or data, e.g. from the LPV application, results in an immediate disconnect from the IoT Hub. The logs on the IoT Hub side give a 400 Bad Request error, followed by an internal server error and a disconnect message. I have no trouble re-connecting after this, however.
My guess is that there is some part of the MQTT message sent by the LPV app that is malformed or missing, but I am unsure how to correct this or even see what it is trying to send. Any and all help would be greatly appreciated.

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[vivekatoffice]

Hi @FLSandberg ,
As per my understanding, you may be missing the MQTT Event Bridge part. I am adding the steps that I followed to test the MQTT Events to Azure IoT Hub from AXIS License Plate Verifier ACAP:

1. Get the correct topicFilter using AXIS Metadata Monitor for ALPV event metadata.

Use this Test button if you don't have the camera on the road with the vehicle 😉

2. Start MQTT Events for ALPV using the the MQTT Event Bridge APIs:

URL

http://{{device}}/axis-cgi/mqtt/event.cgi

Body:

{
    "apiVersion": "1.0",
    "context": "some context",
    "method": "configureEventPublication",
    "params": {
        "eventFilterList": [
            {
                "topicFilter": "tnsaxis:CameraApplicationPlatform/ALPV.AllPlates"
            }
        ]
    }
}

Response:

{
    "apiVersion": "1.2",
    "context": "some context",
    "method": "configureEventPublication",
    "data": {}
}

Snapshot using Postman:

3. Confirm the MQTT subscription

4. Check the MQTT messages on the Azure IoT Hub:

[FLSandberg]

Thank you! I believe part of my problem was that I was not actively running the ALPV app while I was configuring the MQTT settings, which made it impossible to set up the AllPlates event properly, as it does not show up in the list of conditions. Confirming all of the steps above and making doubly sure to put all the slashes in the right place in the topic prefixes (devices/device01/messages/events/) I was now able to add the condition ALPV.AllPlates to the MQTT settings page and telemetry is now received by IoT Hub.