.Net TCP 客户端通信问题

Question

我是网络编程的新手，正试图在 ICE API 测试服务器和我的应用程序之间建立通信。当我尝试登录到服务器时，下面的代码只工作一次。换句话说，当我发送登录消息时，服务器会成功登录回复我。一旦我得到这个，我将下一条消息发送到服务器，但作为回复我得到 0，这意味着服务器已经断开连接。有人可以看一下我的客户逻辑并指出发生上述情况的正确方向吗？请帮我解决这个问题，因为我已经浪费了几天没有结果。谢谢你。

Public Function connect() As Boolean
            bConnected = True
            Dim port As Int32 = Convert.ToInt32("80") 
            Dim server As String = "63.247.113.201" 
            Try
                objClient = New System.Net.Sockets.TcpClient(server, port)
                objClient.NoDelay = False
                objClient.Client.SetSocketOption(SocketOptionLevel.Tcp, SocketOptionName.KeepAlive, 1)
                objClient.GetStream.BeginRead(byReadBuffer, 0, BYTES_TO_READ, New AsyncCallback(AddressOf doRead), Nothing)
            Catch ex As Exception
                RaiseEvent exErr(ex.ToString)
                bConnected = False
            End Try

            Return bConnected
        End Function

Public Function DoTCPRequest(ByVal data As String, ByVal resetSession As Boolean) As String 
            Dim objSw As IO.StreamWriter

            Try
                objSw = New IO.StreamWriter(objClient.GetStream)
                objSw.Write(data & vbCrLf)
                objSw.Flush()
                Console.WriteLine("Sent:" + data)
           Catch ex As Exception
                RaiseEvent exErr(ex.ToString)
            End Try

            objClient.GetStream.BeginRead(byReadBuffer, 0, BYTES_TO_READ, AddressOf Me.doRead, Nothing)
            Return System.Text.Encoding.UTF8.GetString(byReadBuffer, 0, BYTES_TO_READ)
        End Function

      Private Sub doRead(ByVal ar As System.IAsyncResult)
            Dim nTotalRead As Integer
            Try
                Try
                    nTotalRead = objClient.GetStream.EndRead(ar)                     Catch ex As Exception
                    RaiseEvent exErr(ex.ToString)
                End Try

                If nTotalRead > 0 Then
                    Dim szReceivedString As String = System.Text.Encoding.UTF8.GetString(byReadBuffer, 0, nTotalRead)
                    RaiseEvent dataReceived(szReceivedString)
                    Console.WriteLine("Recv1:" + szReceivedString)
                End If

               objClient.GetStream.BeginRead(byReadBuffer, 0, BYTES_TO_READ, New AsyncCallback(AddressOf doRead), Nothing)     

            Catch ex As Exception
                RaiseEvent exErr(ex.ToString)
            End Try

        End Sub

Answer 1

@lberezka，我在代码中看到了一件奇怪的事情。您想查看 DoRead() 方法中的以下代码行吗？

objClient.GetStream.BeginRead(byReadBuffer, 0, BYTES_TO_READ, New AsyncCallback(AddressOf doRead), Nothing) 'Begin the reading again.

理想情况下，在任何异步调用(Begin 类)中，回调句柄应收到答案并尝试使用 End 方法结束调用。在你的情况下 Stream.EndRead。

我在您的代码中看到的是，您一次又一次地递归调用 begin 方法，但我在任何地方都看不到 EndRead。

它给你任何线索吗？