Exception of type 'uPLibrary.Networking.M2Mqtt.Exceptions.MqttClientException' was thrown

Question

I am connecting to the mqtt and I am receiving an un-helpful exception.

Code

string smsTopic = ConfigurationManager.AppSettings["MQTT_SMS_Topic"];
string emailTopic = ConfigurationManager.AppSettings["MQTT_Email_Topic"];
string pushTopic = ConfigurationManager.AppSettings["MQTT_PUSH_Topic"];
string socialTopic = ConfigurationManager.AppSettings["MQTT_SOCIAL_Topic"];

client = new MqttClient("somehostname");
string clientId = Guid.NewGuid().ToString();
client.Connect(clientId);
client.MqttMsgPublishReceived += client_MqttMsgPublishReceived;
client.Subscribe(new string[] { smsTopic, emailTopic, pushTopic, socialTopic }, new byte[] { MqttMsgBase.QOS_LEVEL_EXACTLY_ONCE });

Exception Message

Exception of type 'uPLibrary.Networking.M2Mqtt.Exceptions.MqttClientException' was thrown

Stacktrace of the exception

at uPLibrary.Networking.M2Mqtt.Messages.MqttMsgSubscribe.GetBytes(Byte protocolVersion) in c:\Users\ppatierno\Source\Repos\m2mqtt\M2Mqtt\Messages\MqttMsgSubscribe.cs:line 187
at uPLibrary.Networking.M2Mqtt.MqttClient.Send(MqttMsgBase msg) in c:\Users\ppatierno\Source\Repos\m2mqtt\M2Mqtt\MqttClient.cs:line 1028
at uPLibrary.Networking.M2Mqtt.MqttClient.ProcessInflightThread() in c:\Users\ppatierno\Source\Repos\m2mqtt\M2Mqtt\MqttClient.cs:line 1954
at System.Threading.ThreadHelper.ThreadStart_Context(Object state)
at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
at System.Threading.ThreadHelper.ThreadStart()

I founded a bug on the github, but without solution

The exception Message is not helpful at all, and there is NO inner exception inside it.

Answer 1

I was able to solve this wired exception by changing the following statement

client.Subscribe(new string[] { smsTopic, emailTopic, pushTopic, socialTopic }, new byte[] { MqttMsgBase.QOS_LEVEL_EXACTLY_ONCE });

to

client.Subscribe(new string[] { smsTopic }, new byte[] { MqttMsgBase.QOS_LEVEL_EXACTLY_ONCE });
client.Subscribe(new string[] { emailTopic }, new byte[] { MqttMsgBase.QOS_LEVEL_EXACTLY_ONCE });
client.Subscribe(new string[] { pushTopic }, new byte[] { MqttMsgBase.QOS_LEVEL_EXACTLY_ONCE });
client.Subscribe(new string[] { socialTopic }, new byte[] { MqttMsgBase.QOS_LEVEL_EXACTLY_ONCE });

it appears the mqtt has bug when specify more than one topic at the same time.

Answer 2

Much better:

client.Subscribe(new string[] 
    { smsTopic, emailTopic, pushTopic, socialTopic }, 
    new byte[] { 
         MqttMsgBase.QOS_LEVEL_EXACTLY_ONCE, 
         MqttMsgBase.QOS_LEVEL_EXACTLY_ONCE,
         MqttMsgBase.QOS_LEVEL_EXACTLY_ONCE,
         MqttMsgBase.QOS_LEVEL_EXACTLY_ONCE 
    }
);