Question

我是网络编程的新手，并且正在尝试在ICE API测试服务器和我的应用程序之间建立通信。当我尝试登录服务器时，下面的代码只能运行一次。换句话说，当我发送登录信息时，服务器会通过成功登录回复我。一旦我得到这个，我发送下一条消息到服务器，但作为回复我得到0，这意味着服务器已经断开连接。有人可以看看我的客户逻辑，并指出正确的方向，为什么上面的情况发生。请帮我解决这个问题，因为我已经过了几天没有结果。谢谢。

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，我在代码中看到一件奇怪的事情。是否要在DoRead（）方法中查看以下代码行。

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 kind）中，回调句柄应该接收答案并尝试使用End方法结束调用。在您的情况下Stream.EndRead。

我在你的代码中看到的是你一遍又一遍地递归调用begin方法而且我没有在任何地方看到EndRead。

它能给你任何线索吗？

.Net TCP客户端通信问题

1 个答案: