tcpClient.BeginConnect

 c#:

public bool Test()

{

     using (var tcp = new TcpClient())

     {

         var c = tcp.BeginConnect(IPAddress.Parse("8.8.8.8"), 8080, null, null);

         var success = c.AsyncWaitHandle.WaitOne(TimeSpan.FromSeconds(1));

         if (!success)

         {

             Console.WriteLine("Before cleanup");

             tcp.Close();

             tcp.EndConnect(c);

             Console.WriteLine("After cleanup");

             throw new Exception("Failed to connect.");

         }

     }

     return true;

}

vbnet:

Public Function Test() As Boolean

Using tcp As Object = New TcpClient()

Dim c As Object = tcp.BeginConnect(IPAddress.Parse("8.8.8.8"), 8080, Nothing, Nothing)

Dim success As Object = c.AsyncWaitHandle.WaitOne(TimeSpan.FromSeconds(1))

If Not success Then

Console.WriteLine("Before cleanup")

tcp.Close()

tcp.EndConnect(c)

Console.WriteLine("After cleanup")

Throw New Exception("Failed to connect.")

End If

End Using

Return True

End Function

====

調整用法:

 Public Function Test() As Boolean

        Using tcp As Object = New TcpClient()

            Dim c As Object = tcp.BeginConnect(IPAddress.Parse("192.168.1.78"), 1435, Nothing, Nothing)

            Dim success As Object = c.AsyncWaitHandle.WaitOne(TimeSpan.FromSeconds(1))

            If Not success Then

                tcp.Close()

                Return False

            End If

        End Using

        Return True

    End Function