string hostname = "server1";int portno = 9081;IPAddress ipa = (IPAddress) Dns.GetHostAddresses(hostname)[0];try{ System.Net.Sockets.Socket sock = new System.Net.Sockets.Socket(System.Net.Sockets.AddressFamily.InterNetwork, System.Net.Sockets.SocketType.Stream, System.Net.Sockets.ProtocolType.Tcp); sock.Connect(ipa, portno); if (sock.Connected == true) // Port is in use and connection is successful MessageBox.Show("Port is Closed"); sock.Close();}catch (System.Net.Sockets.SocketException ex){ if (ex.ErrorCode == 10061) // Port is unused and could not establish connection MessageBox.Show("Port is Open!"); else MessageBox.Show(ex.Message);}}