M2MQTT Argument Exception: unsupported HMAC

It looks like you are encountering an error message related to M2MQTT, which is a .NET library for MQTT communication. The error message “unsupported HMAC” suggests that there is an issue with the Hash-based Message Authentication Code (HMAC) being used in your MQTT communication.

HMAC is a way to verify the integrity and authenticity of a message by using a secret key and a hash function. If you are seeing this error message, it could be because the HMAC algorithm being used is not supported by the M2MQTT library, or there may be a problem with the implementation of the HMAC calculation.

To troubleshoot this issue, you may want to try the following:

1. Check the documentation for the M2MQTT library to make sure that the HMAC algorithm you are using is supported.
2. Check your code to ensure that you are using the correct parameters for the HMAC calculation, including the correct secret key and hash function.
3. Make sure that you are using the latest version of the M2MQTT library, as older versions may not support certain HMAC algorithms.
4. If you are using a third-party library to calculate the HMAC, make sure that it is compatible with the M2MQTT library.