messaging_service.dart

import 'package:mqtt_client/mqtt_client.dart';
import 'package:rxdart/rxdart.dart';

class MessagingService {  
  /// Subscribes to the given topic and produces a stream of received updates from the message
  /// broker matching this topic. You can also pass [MqttQos] which defaults to atLeastOnce.
  ///
  /// This method returns a stream of [MqttMessage] instances.
  Stream<MqttMessage> updatesFor(String topic, [MqttQos qos = MqttQos.atLeastOnce]) {
    ...
  }
  
  /// Publishes a message to the message broker. You should pass a topic and serialized
  /// message data in JSON format. You can also pass [MqttQos] which defaults to atLeastOnce.
  ///
  /// This method returns a [Future] of message identifer [int] assigned to the message.
  Future<int> request(String topic, String jsonData, [MqttQos qos = MqttQos.atLeastOnce]) {
    ...
  }
}