gistfile1.cs

private void ExecutePortScan(string host, int port, int timeout)
{
	using (TcpClient tcpClient = new TcpClient())
	{
		DateTime timer =  DateTime.Now;
		TimeSpan time;
		IAsyncResult result = tcpClient.BeginConnect(host, port, null, null);

		WaitHandle timeoutHandler = result.AsyncWaitHandle;
		try
		{
			if (!result.AsyncWaitHandle.WaitOne (new TimeSpan (0, 0, timeout), false)) {
				tcpClient.Close ();
				time = DateTime.Now - timer;
				Console.WriteLine (time.ToString () + " " + "Timeout expired");
			} else {
				tcpClient.EndConnect(result);
				time = DateTime.Now - timer;
				Console.WriteLine(time.ToString() + " " + "Success");
			}
		}
		catch (Exception ex)
		{
			time = DateTime.Now - timer;
			Console.WriteLine(time.ToString() + " " +  ex);
		}
		finally
		{
			timeoutHandler.Close();
		}
	}
}