高手请进：多线程异步的一个问题

Question

主函数中，通过新开线程来监听多个客户端的连接
TcpListener listener = new TcpListener(localEndPoint);
listener.Start();
while (true) 
{
Thread th = new Thread(new ThreadStart(ListenClient));
th.Start();
th.Join();
}public static void ListenClient() 
{
TcpClient client = listener.AcceptTcpClient(); 
NetworkStream ns = client.GetStream(); 
StateObject state = new StateObject();
state.nsClient = ns;
ns.BeginRead(state.buffer,0,StateObject.BufferSize,new AsyncCallback(ReadCallback),state);
}public static void ReadCallback(IAsyncResult ar) 
{
StateObject state = (StateObject) ar.AsyncState;
NetworkStream ns  = state.nsClient;   
try
{
int iRead = ns.EndRead(ar); 。
    
}
现在的问题是，在客户端连接成功之后，还没有发送数据之前，就会执行到ReadCallback，于是在ns.EndRead处就会报错：“无法读取数据流”。
很奇怪为什么会出现这个问题，按说只有客户端发送数据之后才会出现这个问题。

Answer 1

NetworkStream ns = client.GetStream(); 
StateObject state = new StateObject();
把这段放在一个等待接收的循环中.当接收长度达到,或者接到结束符,才跳出往后执行.

Answer 2

Public Sub New(ByVal client As TcpClient)
        Me.client = client
        Me.client.GetStream.BeginRead(readBuffer, 0, BUFFER_SIZE, AddressOf StreamReceiver, Nothing)
    End SubPrivate Sub StreamReceiver(ByVal ar As IAsyncResult)
        Dim BytesRead As Integer
        Dim strMessage As String        Try
            SyncLock client.GetStream
                BytesRead = client.GetStream.EndRead(ar)
            End SyncLock            If BytesRead < 1 Then
                Exit Sub
            End If            If Me.transferStatus = TRANSFER_STATUS.ASCII Then
                strMessage = Encoding.ASCII.GetString(readBuffer, 0, BytesRead)                Select Case strMessage.Split(Chr(124))(0)
                    Case "FILE"
                        Me.transferStatus = TRANSFER_STATUS.Binary
                        fileSize = CInt(strMessage.Split(Chr(124))(1))
                       fileWritedSize = 0
                        RaiseEvent TransferFileBegin(Me, fileName)
                        fileStream = New IO.FileStream(fileName, IO.FileMode.OpenOrCreate, IO.FileAccess.Write)
                    Case "DOWN"
                        SendFile(strMessage.Split(Chr(124))(1))
                    Case Else
                          RaiseEvent LineReceived(Me, strMessage)
                End Select            Else
                 fileWritedSize = fileWritedSize + BytesRead
                Me.fileStream.Write(readBuffer, 0, BytesRead)
                Me.fileStream.Flush()                 If fileWritedSize >= fileSize Then
                    Me.fileStream.Close()
                    Me.transferStatus = TRANSFER_STATUS.ASCII
                    RaiseEvent TransferFileEnd(Me, fileName)
                End If
            End If            SyncLock client.GetStream
                client.GetStream.BeginRead(readBuffer, 0, BUFFER_SIZE, AddressOf StreamReceiver, Nothing)
            End SyncLock
        Catch e As Exception
        End Try
    End Sub