Extend the mDNS package with a native extension used on Mac OS

pkg/mdns/lib/src/native_protocol_client.dart

-// Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
+// Copyright (c) 2015, the Fletch project authors. Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
-// BSD-style license that can be found in the LICENSE file.
+// BSD-style license that can be found in the LICENSE.md file.
+
+library mdns.src.native_protocol_client;
 
 import 'dart:async';
 import 'dart:collection';
 import 'dart:io';
-import 'dart:typed_data';
 
+import 'package:mdns/mdns.dart';
 import 'package:mdns/src/constants.dart';
 import 'package:mdns/src/lookup_resolver.dart';
 import 'package:mdns/src/packet.dart';
 
-/// Client for DNS lookup using the mDNS protocol.
-///
-/// This client only support "One-Shot Multicast DNS Queries" as described in
-/// section 5.1 of https://tools.ietf.org/html/rfc6762
-class MDnsClient {
+// Implementation of mDNS client using the native protocol.
+class NativeProtocolMDnsClient implements MDnsClient {
   bool _starting = false;
   bool _started = false;
   RawDatagramSocket _incoming;
   final List<RawDatagramSocket> _sockets = <RawDatagramSocket>[];
   final LookupResolver _resolver = new LookupResolver();
 
   /// Start the mDNS client.
   Future start() async {
     if (_started && _starting) {
       throw new StateError('mDNS client already started');
@@ skipping 15 matching lines @@
 
       // Join multicast on this interface.
       _incoming.joinMulticast(mDnsAddress, interface);
     }
     _incoming.listen(_handleIncoming);
 
     _starting = false;
     _started = true;
   }
 
-  /// Stop the mDNS client.
   void stop() {
     if (!_started) return;
     if (_starting) {
       throw new StateError('Cannot stop mDNS client wile it is starting');
     }
 
     _sockets.forEach((socket) => socket.close());
     _incoming.close();
 
     _started = false;
   }
 
-  /// Lookup [hostname] using mDNS.
-  ///
-  /// The `hostname` must have the form `single-dns-label.local`,
-  /// e.g. `printer.local`.
-  ///
-  /// If no answer has been received within the specified [timeout]
-  /// this method will complete with the value `null`.
   Future<InternetAddress> lookup(
       String hostname, {Duration timeout: const Duration(seconds: 5)}) {
     if (!_started) {
       throw new StateError('mDNS client is not started');
     }
 
     // Add the pending request before sending the query.
     var future = _resolver.addPendingRequest(hostname, timeout);
 
     // Send the request on all interfaces.
     List<int> packet = encodeMDnsQuery(hostname);
     for (int i = 0; i < _sockets.length; i++) {
       _sockets[i].send(packet, mDnsAddress, mDnsPort);
     }
 
     return future;
   }
 
   // Process incoming datagrams.
   _handleIncoming(event) {
     if (event == RawSocketEvent.READ) {
       var data = _incoming.receive();
       var response = decodeMDnsResponse(data.data);
       if (response != null) {
         _resolver.handleResponse(response);
       }
     }
   }
 }
-
-// Simple standalone test.
-main() async {
-  var client = new MDnsClient();
-  await client.start();
-  var address = await client.lookup('raspberrypi.local');
-  client.stop();
-  print(address);
-}