TopicsQosLevelsNotMatch exception in MqttMsgSubscribe not being raised at user code level

[patrickgardella]

I made a mistake in trying some of the demo code, in that I was subscribing to two queues, but only passing in a single QOS level.

            string clientId = Guid.NewGuid().ToString();
            client.Connect(clientId);

            string[] topic = { "sensor/temp", "sensor/humidity" };

            byte[] qosLevels = { MqttMsgBase.QOS_LEVEL_EXACTLY_ONCE };

This caused an exception to be thrown:

uPLibrary.Networking.M2Mqtt.Exceptions.MqttClientException was unhandled
Message: An unhandled exception of type 'uPLibrary.Networking.M2Mqtt.Exceptions.MqttClientException' occurred in M2Mqtt.Net.dll

(I was using the NuGet 4.3.0 code for this.) I couldn't catch this exception and handle it, because the true exception does not make it to the user's level. Nor could I find out what the actual exception was.

When I compiled the m2mqtt code from GitHub, I debugged it and found that MqttMsgSubscribe.GetBytes() was throwing a TopicsQosLevelsNotMatch exception:

uPLibrary.Networking.M2Mqtt.Exceptions.MqttClientException occurred
  HResult=-2146233088
  Message=Exception of type 'uPLibrary.Networking.M2Mqtt.Exceptions.MqttClientException' was thrown.
  Source=M2Mqtt.Net
  StackTrace:
       at uPLibrary.Networking.M2Mqtt.Messages.MqttMsgSubscribe.GetBytes(Byte protocolVersion) in C:\Users\Patrick Gardella\Documents\Visual Studio 2015\Projects\paho.mqtt.m2mqtt\M2Mqtt\Messages\MqttMsgSubscribe.cs:line 187
  InnerException: 

It is the MqttClient.Send() that ignores the throw exceptions: M2Mqtt.Net.dll!uPLibrary.Networking.M2Mqtt.MqttClient.Send(uPLibrary.Networking.M2Mqtt.Messages.MqttMsgBase msg) Line 1029

Clearly I can avoid this now that I know what was wrong, but it would be good to either log the exception or raise it to the user's level.

Thanks for all your great work on this!

Patrick+

[HakamFostok]

I am facing the same problem, and I was able to solve it, here is the solution which could help others
http://stackoverflow.com/questions/39917469/

BUT, I think this really should be considered in the MQTT library, and the library should check for this case and throw an appropriate exception with a helpful message to help the user knowing what is going wrong.
Throwing this general exception make the developer confused about what he/she did wrong.