private void btn_start_Click(object sender, RoutedEventArgs e)
 {
     if (Init())
     {
         client.Command();
         btn_start.IsEnabled           = false;
         txt_drone_ip.IsEnabled        = false;
         btn_ip_list.IsEnabled         = false;
         check_joystick_mode.IsEnabled = false;
         menu_curve_editor.IsEnabled   = true;
         menu_query.IsEnabled          = true;
     }
 }