通过 TCP 发送大字符串时丢失数据。（客户端服务器）答案

【问题标题】：Missing data while sending large string over TCP. (client/server)通过 TCP 发送大字符串时丢失数据。（客户端服务器）
【发布时间】：2012-05-16 21:46:48
【问题描述】：

我有一个客户端/服务器应用程序，其中服务器在 java 中，客户端在 Vb.net 中。

当我从客户端向服务器发送大字符串时，没有收到完整的文本。请帮忙。

代码附在下面。

客户端--VB.net-

      Try
         Dim clientSocket As New System.Net.Sockets.TcpClient()

        ' msg("Client Started")
        clientSocket.Connect(StrIP_Add, intPort)
        clientSocket.SendBufferSize=104857600
        '6511 6522
        ' Label1.Text = "Client Socket Program - Server Connected ..."

        Dim serverStream As NetworkStream = clientSocket.GetStream()
        Dim outStream(104857600) As Byte

        ' MsgBox(strValidator.Trim.Length)

        outStream = System.Text.Encoding.ASCII.GetBytes(strValidator.Trim)
        ' Dim outStream As Byte() = "sdsfd"
        System.Threading.Thread.Sleep(2000)
        serverStream.Write(outStream, 0, outStream.Length)
        System.Threading.Thread.Sleep(2000)
        serverStream.Flush()

        Dim inStream(104857600) As Byte
        serverStream.Read(inStream, 0, outStream.Length) '104857600) ' CInt(clientSocket.ReceiveBufferSize))
        Dim returndata As String = _
        System.Text.Encoding.ASCII.GetString(inStream)
        '  msg("Data from Server : " + returndata)
        clientSocket.Close()

    Catch ex As Exception
        ' VikUcMsg.AddMessage("<b><u>" & Page.Title & "</u></b><br><br>" & "No Connectivity on the port :" & intPort, enmMessageType.Error)


    End Try

服务器--Java

BufferedInputStream RecievedBuffer = new BufferedInputStream(
                TCPIP_Client_SOCKET.getInputStream());
        InputStreamReader RecievedInputStreamReader = new InputStreamReader(
                RecievedBuffer);

        System.out.println(RecievedBuffer.toString().length());
        //char[] RecievedChars = new char[TCPIP_Client_SOCKET
                //.getReceiveBufferSize()];

        char[] RecievedChars = new char[100000];
        //Thread.sleep(5000);
        RecievedInputStreamReader.read(RecievedChars);
        //Thread.sleep(5000);
        String strRecievedData=null;
        //Thread.sleep(5000);
        strRecievedData = new String( RecievedChars ).trim();
        //strRecievedData = RecievedChars.;
        Thread.sleep(5000);
        if (strRecievedData!=null)
        {
            System.out.println(strRecievedData);
                         }

strRecievedData 一直只有 havig 8192。

【问题讨论】：

标签： java vb.net tcp

【解决方案1】：

简短的回答是，从套接字读取时必须循环，因为无法保证每次尝试读取时会收到多少字节。

伪代码：

while (!msgCompleted && !overallTimeout)
{
   bytesRead = netstream.Read(readBuffer);

   if (bytesRead > 0)
   {
      // here append readBuffer to msgBuffer from offset to offset+bytesRead 

      offset += bytesRead // update offset so you can keep appending

     // inspect the msgBuffer to see if the message is completed
   }

}

话虽如此，您的代码中还有许多其他问题。比如……

你在这里分配一个 104857601（不是 104857600）字节缓冲区：

Dim outStream(104857600) As Byte

然后丢弃该缓冲区并将其替换为从 strValidator 重新获得的任何内容：

outStream = System.Text.Encoding.ASCII.GetBytes(strValidator.Trim)

为了替换它而预先分配它没有意义。

另一个...

你分配了一个特定长度的输入缓冲区：

Dim inStream(104857600) As Byte

然后使用不同缓冲区的长度读入该缓冲区：

serverStream.Read(inStream, 0, outStream.Length)

根据长度，这很容易出错。

您还需要循环读取此 VB 读取，就像读取 Java 读取一样。

【讨论】：