anchor.diff:    final _responders = <String, Completer<Map<String, List<Message>>>>{};
     final _timers = <String, Completer<bool>>{};
     Service service;
  -  int messageQueueMaxLength = 10;
     Duration timeout = const Duration(minutes: 2);
     Duration heartbeat = const Duration(seconds: 10);
     void Function(String id, String topic, ServiceContext context) onSubscribe;
  
positive.code:     for (final id in _messages.keys) {
        if (_messages[id].containsKey(topic)) {
          final messages = _messages[id][topic];
          if (messages.length < messageQueueMaxLength) {
            messages.add(Message(data, from));
            _response(id);
            result[id] = true;
          } else {
            result[id] = false;
          }
        }
      }
      return result;
  
negative.code:   bool unicast(dynamic data, String topic, String id, [String from = '']) {
      if (_messages.containsKey(id) && _messages[id].containsKey(topic)) {
        final messages = _messages[id][topic];
        messages.add(Message(data, from));
        _response(id);
        return true;
      }
      return false;
    }
  