TCP读写问题.net答案

【问题标题】：TCP read write issue .netTCP读写问题.net
【发布时间】：2012-07-31 22:41:03
【问题描述】：

我正在使用以下代码从特定服务器发送消息

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
    send("Hello there")
    TextBox1.Text = TextBox1.Text + "Send Successful"
End Sub

Public Sub send(ByVal data As String)
    Dim tcpClient As New TcpClient()
    Try
        tcpClient.Connect("10.xxx.xx.xx", 7000)
        TextBox1.text = TextBox1.Text + "Conneecte"
    Catch e As Exception
        Console.WriteLine(e)
    End Try
    If tcpClient.Connected Then
        Dim networkStream As NetworkStream = tcpClient.GetStream()
        Dim streamWriter As New StreamWriter(networkStream)
        Console.WriteLine("Messege {0} to {1}", data, tcpClient.Client.RemoteEndPoint)
        streamWriter.WriteLine(data)
        streamWriter.Flush()
        tcpClient.Close()
    End If
End Sub

发送成功。

下面的代码是从另一个系统读取的。并且代码挂在do while循环中

Private Sub Button3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button3.Click
    Dim tcpClient As New System.Net.Sockets.TcpClient()
    Try
        tcpClient.Connect("10.xxx.xx.xx", 7000)
        Dim networkStream As NetworkStream = tcpClient.GetStream()
        If networkStream.CanWrite And networkStream.CanRead Then
            'Dim sendBytes As [Byte]() = Encoding.ASCII.GetBytes("$gimme")
            'networkStream.Write(sendBytes, 0, sendBytes.Length)
            ' 'Read the NetworkStream into a byte buffer.
            Do
            Loop Until networkStream.DataAvailable
            Dim bytes(tcpClient.ReceiveBufferSize) As Byte
            networkStream.Read(bytes, 0, CInt(tcpClient.ReceiveBufferSize))
            Dim returndata As String = Encoding.ASCII.GetString(bytes)
            ''Label1.Text = returndata
            tcpClient.Close()
        Else
            If Not networkStream.CanRead Then
                tcpClient.Close()
            Else
                If Not networkStream.CanWrite Then
                    tcpClient.Close()
                End If
            End If
        End If
    Catch ex As Exception
        'sLabel1.Text = "Exception Caught"
    End Try
End Sub

而且代码挂在这里在读取部分

做循环直到 networkStream.DataAvailable

我在这里做错了什么？

【问题讨论】：

如果你写行，你应该读行。您的发送者和接收者的逻辑不匹配。
另外，您一直在循环，直到设置了 DataAvailable 标志，但您的代码中没有设置该标志。例如，您不拨打Poll。仅当您执行某些更改其状态的操作时，连接对象才会更改状态。（如读、写、连接、关闭、轮询等。）
@DavidSchwartz.. 我只是将 Read 方法更改为 'Dim tcpClient As New TcpClient() Try tcpClient.Connect("10.230.10.33", 7000) TextBox1.Text = TextBox1.Text + "Conneecte " Catch ee As Exception Console.WriteLine(ee) End Try If tcpClient.Connected Then Dim networkStream As NetworkStream = tcpClient.GetStream() Dim reader As New IO.StreamReader(networkStream) Dim str As String = reader.ReadLine() reader。 Close() tcpClient.Close() End If' 读取失败

标签： .net tcpclient tcplistener

【解决方案1】：

根据以下代码，您的代码逻辑似乎有缺陷。

' Examples for CanRead, Read, and DataAvailable.
' Check to see if this NetworkStream is readable.
If myNetworkStream.CanRead Then
   Dim myReadBuffer(1024) As Byte
       Dim myCompleteMessage As StringBuilder = New StringBuilder()
   Dim numberOfBytesRead As Integer = 0

   ' Incoming message may be larger than the buffer size.
   Do
      numberOfBytesRead = myNetworkStream.Read(myReadBuffer, 0, myReadBuffer.Length)
           myCompleteMessage.AppendFormat("{0}", Encoding.ASCII.GetString(myReadBuffer, 0, numberOfBytesRead))
   Loop While myNetworkStream.DataAvailable

   ' Print out the received message to the console.
       Console.WriteLine(("You received the following message : " + myCompleteMessage.ToString()))
Else
   Console.WriteLine("Sorry.  You cannot read from this NetworkStream.")
End If

我建议你再考虑一下NetworkStream.DataAvailable Property

【讨论】：

是的。 can read 属性为 true，但系统在 .Read 方法处挂起，发送的消息为“Test message”

【解决方案2】：

问题是没有已知的方法可以立即读取所有字节，而不会阻塞 read()。要以 inputstream.ReadLine() 的方式读取一行，最好逐个字符地读取，直到读取到行尾字符：

Function readln(ByRef inputstream as Stream) as String
 Dim r as String = ""
 do
  Dim c as Char = Chr(inputstream.Read())
  If c = vbCr Then Exit loop    'vbCr or vbLf depending on application'
  r += c
 loop
 Return r
End Function

不是很好但很实用。并且在数据到达缓慢或延迟时不会消耗 CPU 性能。 inputstream.Read() 为您阻塞，直到有字符可用。

【讨论】：