未处理TCP的Timeoutexception

Question

我从网站上获取此代码，因为VS 2010不支持TCP连接的超时：

Private Function ConnectWithTimeout() As Boolean
    Dim ar As IAsyncResult = TCPClient.BeginConnect(IPAddress, TCPPort, Nothing, Nothing)
    Dim wh As System.Threading.WaitHandle = ar.AsyncWaitHandle

    Try
        If Not ar.AsyncWaitHandle.WaitOne(TimeSpan.FromSeconds(2), False) Then
            TCPClient.Close()
            TCPClient = New System.Net.Sockets.TcpClient
            Throw New TimeoutException()
        End If
    Catch ex As Exception
        ThrowError("Timeout on connecting to " & IPAddress & " at port " & TCPPort & ".")
        Return False
    Finally
        wh.Close()
    End Try

    Return True
End Function

它工作正常，但每次，它在调试输出上给我这个：

“发生在'System.TimeoutException'类型的第一次机会异常”

即使我抓住所有例外。有没有办法摆脱这个异常消息，因为它被处理？

我试过这个：

    Dim connectDone As New System.Threading.AutoResetEvent(False)
    TCPClient.BeginConnect(IPAddress, TCPPort, New AsyncCallback(Sub(ar As IAsyncResult)
                                                                     TCPClient.EndConnect(ar)
                                                                     connectDone.Set()
                                                                 End Sub), TCPClient)
    'client.BeginConnect("127.0.0.1", 80, new AsyncCallback(delegate( IAsyncResult ar ) { client.EndConnect( ar );  connectDone.Set(); }), client);

    If Not connectDone.WaitOne(2000) Then
        Debug.WriteLine("TIMEOUT")
        Return False
    End If

    Return True

但是它在beginconnect行上给了我InvalidOperationException：当同一个Socket上正在进行另一个异步操作时，无法调用BeginConnect。

Answer 1

Private Function ConnectWithTimeout() As Boolean
    Dim ar As IAsyncResult 
    Dim wh As System.Threading.WaitHandle  

    Try
          ar = TCPClient.BeginConnect(IPAddress, TCPPort, Nothing, Nothing)
          wh = ar.AsyncWaitHandle
    Cath ex as Exception
          'Code to catch exception
    End Try

    Try
        If Not ar.AsyncWaitHandle.WaitOne(TimeSpan.FromSeconds(2), False) Then
            TCPClient.Close()
            TCPClient = New System.Net.Sockets.TcpClient
            Throw New TimeoutException()
    End If
    Catch ex As Exception
        ThrowError("Timeout on connecting to " & IPAddress & " at port " & TCPPort & ".")
        Return False
    Finally
        wh.Close()
    End Try

    Return True
End Function