anchor.diff:      ..add(new NavRadioPage(nav1))
       ..add(new NavRadioPage(nav2))
       ..add(new AltitudePage());
  +
  +  var send = await RawDatagramSocket.bind(InternetAddress.ANY_IP_V4, 1236);
  +  props.onUpdate.listen((update) {
  +    log.info('sending: $update to 1235');
  +    send.send(UTF8.encode(update), InternetAddress.LOOPBACK_IP_V4, 1235);
  +  });
  +
  +  var sock = await RawDatagramSocket.bind(InternetAddress.ANY_IP_V4, 1234);
  +  await for (var event in sock) {
  +    //print(event);
  +    if (event == RawSocketEvent.READ) {
  +      Datagram dg = sock.receive();
  +      props.parse(dg.data);
  +    }
  +  }
   }
   
   class NavRadioPage extends Page {
  
positive.code:     print("Error($e) listening to $port: ${e.stackTrace}");
      exit(-1);
    }
  
    var proto = new ArdProto(port);
    var display = new Display(proto);
  
negative.code: // limitations under the License.
  
  import 'dart:async';
  import 'dart:convert';
  import 'dart:io';
  
  import 'package:ardknob/ardproto.dart';
  import 'package:ardknob/display.dart';
  import 'package:ardknob/flightgear.dart';
  import 'package:ardknob/pages.dart';
  
  import 'package:logging/logging.dart';
  