using System.Net;  if(!string.IsNullOrEmpty(txtPort.Text))  {      IPAddress ip = IPAddress.Parse(txtIp.Text);      IPEndPoint point=new IPEndPoint(ip,int.Parse(txtPort.Text));      try      {          TcpClient tcp=new TcpClient();          tcp.Connect(point);          MessageBox.Show("端口打开");      }catch(Exception ex)      {          MessageBox.Show(ex.Message);      }  }