Re-land "Extend the mDNS package with a native extension used on Mac OS"

pkg/mdns/lib/src/native_protocol_client.dart

Index: pkg/mdns/lib/src/native_protocol_client.dart
diff --git a/pkg/mdns/lib/mdns.dart b/pkg/mdns/lib/src/native_protocol_client.dart
similarity index 74%
copy from pkg/mdns/lib/mdns.dart
copy to pkg/mdns/lib/src/native_protocol_client.dart
index f707136d4c865cb33b8b6f39c022af0af5fbd5f7..23854300ee9281e44c4dac70c3755474579346bb 100644
--- a/pkg/mdns/lib/mdns.dart
+++ b/pkg/mdns/lib/src/native_protocol_client.dart
@@ -1,21 +1,20 @@
-// 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;
@@ -51,7 +50,6 @@ class MDnsClient {
     _started = true;
   }
 
-  /// Stop the mDNS client.
   void stop() {
     if (!_started) return;
     if (_starting) {
@@ -64,13 +62,6 @@ class MDnsClient {
     _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) {
@@ -100,12 +91,3 @@ class MDnsClient {
     }
   }
 }
-
-// Simple standalone test.
-main() async {
-  var client = new MDnsClient();
-  await client.start();
-  var address = await client.lookup('raspberrypi.local');
-  client.stop();
-  print(address);
-}