How can I replace the use of wildcards for subscription to an IoT Hub pseudo topic

Question

I require assistance in analyzing other tools or solutions provided by Azure that could help resolve the issue with my Modicon M262 PLC device, which is unable to use wildcard subscriptions for C2D communication, such as:

devices/deviceID/messages/devicebound/#

Currently, I am researching other services like Event Grid, but subscribing the PLC would require a certificate, which would be a last resort.

What other options might we have? Thank you very much, I will await your response.

Best regards from Chile!

Answer 1

Hello @Marcos Moraga ,

welcome to this moderated Azure community forum.

The Azure IoT Hub supports MQTT to communicate but the topics are all fixed to support the registry device twin.

If devices want to use their own topics or do not want to connect the way the IoT Hub dictates, the EventGrid MQTT broker is a good alternative.

The EventGrid MQTT broker supports plain MQTT(S) with flexible topic usage where you can manage which device is able to use which (groups of) topics for publish or subscribing.

At this moment, supported authentication modes are:

• Certificates issued by a Certificate Authority (CA)
• Self-signed client certificate - thumbprint
• Microsoft Entra ID token

This is demonstrated with multiple programming language libraries, MQTTX and NodeRED.

If this doesn't work for your PLC, see if you can add an Edge solution in between for eg. protocol translation. Check out Azure IoT Edge.

If you wish other ways to authenticate, you can always add your wish here.

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