anchor.diff:  /// [MDnsClient.stop] must be called when done to clean up resources.
   ///
   /// This client only support "One-Shot Multicast DNS Queries" as described in
  -/// section 5.1 of https://tools.ietf.org/html/rfc6762
  +/// section 5.1 of [RFC 6762](https://tools.ietf.org/html/rfc6762).
   class MDnsClient {
     bool _starting = false;
     bool _started = false;
  
positive.code:   }
  
    /// Lookup a [ResourceRecord], potentially from cache.
    Stream<ResourceRecord> lookup(int type, String name,
        {Duration timeout = const Duration(seconds: 5)}) {
      if (!_started) {
        throw StateError('mDNS client is not started.');
      }
  
negative.code:         _resolver.addPendingRequest(type, name, timeout);
  
      // Send the request on all interfaces.
      final List<int> packet = encodeMDnsQuery(
        name,
        type: type,
        multicast: multicast,
      );
      for (RawDatagramSocket socket in _sockets) {
        socket.send(packet, _mDnsAddress, mDnsPort);
      }
  