How to find the open and closed port list

public void ScanPort(string hostip,int startport,int endport)
        {
            for (int i = startport; i <= endport; i++)
            {
                lblMessage.Text = "Scanner: Scanning Port: " + i;
                Port = i;
//Gets main IP of host
                System.Net.IPAddress ip = System.Net.Dns.GetHostEntry(hostip).AddressList[0]; 
                IPEndPoint ipEnd = new IPEndPoint(ip, Port);
                //Creates a new socket.
                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);
                try //Tests the port by trying to connect.
                {
                    _Sock.Connect(ipEnd);
                }
                catch //Catches the error if it can not connect.
                {
                }
                if (_Sock.Connected == true) //Checks if socket is connected or not
                {
                    listOpened.Items.Add(Port.ToString()); //Adds to opened list if socket connected
                    listOpened.EnsureVisible(listOpened.Items.Count - 1);
                }
                else
                {
                    listClosed.Items.Add(Port.ToString()); //Adds to Closed list if socket is not connected
                    listClosed.EnsureVisible(listClosed.Items.Count - 1);
                }
                _Sock.Close(); //Close the socket
            }
            MessageBox.Show("All Ports Scanned Completed!", "", MessageBoxButtons.OK, MessageBoxIcon.Information);
        }