MQTT连接提示：OnError原因:“请求结束，错误!”异常:网络错误!TCP连接在收到任何数据之前就关闭了!

错误描述

错误日志

OnError reason: 
'Request Finished with Error! Exception: Network error!
 TCP Connection got closed before receiving any data! 
 at BestHTTP.HTTPResponse.Receive  

 OnDisconnected - code: UnspecifiedError,
  reason: 'Request Finished with Error! Exception: Network error!
   TCP Connection got closed before receiving any data!  

Unity的运行状态下连接MQTT服务器，是用的是WebSocket连接就会提示，下面是我的连接代码（错误的）。

        ConnectionOptionsBuilder connectionOptionsBuilder;
        connectionOptionsBuilder = new ConnectionOptionsBuilder()
             .WithWebSocket(hostName, port)
             .WithProtocolVersion(SupportedProtocolVersions.MQTT_3_1_1);
             
        client = new MQTTClientBuilder().WithOptions(connectionOptionsBuilder)
                           .WithEventHandler(OnConnected)
                           .WithEventHandler(OnDisconnected)
                           .WithEventHandler(OnStateChanged)
                           .WithEventHandler(OnError)
                         .CreateClient();

解决方式

在编辑器下是用TCP连接

        ConnectionOptionsBuilder connectionOptionsBuilder;
     connectionOptionsBuilder = new ConnectionOptionsBuilder()
        .WithTCP(hostName, port)
        .WithProtocolVersion(SupportedProtocolVersions.MQTT_3_1_1);

   client = new MQTTClientBuilder().WithOptions(connectionOptionsBuilder)
                      .WithEventHandler(OnConnected)
                      .WithEventHandler(OnDisconnected)
                      .WithEventHandler(OnStateChanged)
                      .WithEventHandler(OnError)
                    .CreateClient();

在WebGL下是用WebSocket连接

   ConnectionOptionsBuilder connectionOptionsBuilder;
         connectionOptionsBuilder = new ConnectionOptionsBuilder().
            WithWebSocket(hostName,port).
            WithTLS()
            .WithProtocolVersion(SupportedProtocolVersions.MQTT_3_1_1);

 client = new MQTTClientBuilder().WithOptions(connectionOptionsBuilder)
                    .WithEventHandler(OnConnected)
                    .WithEventHandler(OnDisconnected)
                    .WithEventHandler(OnStateChanged)
                    .WithEventHandler(OnError)
                  .CreateClient();