类型为“uPLibrary.Networking.M2Mqtt.Exceptions.MqttClientException”的异常被抛出

Question

我正在连接到 mqtt，我收到了一个无用的异常。

代码

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 });

异常消息

抛出“uPLibrary.Networking.M2Mqtt.Exceptions.MqttClientException”类型的异常

异常的堆栈跟踪

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()

我在github上发现了一个bug，但是没有解决方案

异常消息根本没有帮助，里面没有内部异常。

Answer 1

我能够通过更改以下语句来解决此有线异常

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

到

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 });

同时指定多个主题时出现

mqtt

的bug

Answer 2

好多了：

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 
    }
);

Answer 3

我关注这个博客。 https://www.hivemq.com/blog/mqtt-client-library-encyclopedia-m2mqtt

如果你阅读订阅部分

client.Subscribe( )

需要两个数组作为输入参数：前者是你想要订阅的

topics

列表，后者是相关的QoS级别列表（每个主题一个）.

所以这意味着您需要通过服务质量（QoS）每个主题的级别。

这将解决您的问题。

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 });

Answer 4

主题数组的长度应与 QoS 级别数组的长度匹配。

这段代码

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 });

可以转换成这个代码

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 });