MissionPlanner.temp.but_mavserialport_Click C# (CSharp) Method

        private void but_mavserialport_Click(object sender, EventArgs e)
        {
            if (comport != null)
            {
                comport.Close();
                if (client != null && client.Connected)
                {
                    client.Close();
                }

                if (listener != null)
                {
                    listener.Stop();
                }
                return;
            }

            try
            {
                comport = new MAVLinkSerialPort(MainV2.comPort, MAVLink.SERIAL_CONTROL_DEV.GPS1);

                if (listener != null)
                {
                    listener.Stop();
                    listener = null;
                }

                listener = new TcpListener(IPAddress.Any, 500);

                listener.Start();

                listener.BeginAcceptTcpClient(DoAcceptTcpClientCallback, listener);
            }
            catch (Exception ex)
            {
                CustomMessageBox.Show(ex.ToString(), Strings.ERROR);
            }
        }