Sending SMS via GSM modem in ASP.Net

public void SendSMS(string phoneNo, string message)
        {
            System.IO.Ports.SerialPort port = new System.IO.Ports.SerialPort("COM13", 115200, System.IO.Ports.Parity.None, 8, System.IO.Ports.StopBits.One);
            try
            {
                port.Open();
                port.Write("AT\r\n");
                System.Threading.Thread.Sleep(1000);
                port.WriteLine("AT+CMGF=1\r\n");
                System.Threading.Thread.Sleep(1000);
                //port.WriteLine("AT+CMGS=\"+60121212121\"\r\n");
                port.WriteLine("AT+CMGS=\"" + phoneNo + "\"\r\n");
                System.Threading.Thread.Sleep(1000);
                //port.WriteLine("Testing SMS\r\n" + '\x001a');
                port.WriteLine(message + "\r\n" + '\x001a');
                return true;
            }
            catch
            {
                return false;
            }
            finally
            {
                port.Close();
            }
        }