mqtt_browser_client.dart

/*
 * Package : mqtt_client
 * Author : S. Hamblett <steve.hamblett@linux.com>
 * Date   : 31/05/2017
 * Copyright :  S.Hamblett
 */

import 'dart:async';
import 'package:mqtt_client/mqtt_client.dart';
import 'package:mqtt_client/mqtt_browser_client.dart';

/// An annotated simple subscribe/publish usage example for mqtt_browser_client. Please read in with reference
/// to the MQTT specification. The example is runnable.

/// First create a client, the client is constructed with a broker name, client identifier
/// and port if needed. The client identifier (short ClientId) is an identifier of each MQTT
/// client connecting to a MQTT broker. As the word identifier already suggests, it should be unique per broker.
/// The broker uses it for identifying the client and the current state of the client. If you don’t need a state
/// to be hold by the broker, in MQTT 3.1.1 you can set an empty ClientId, which results in a connection without any state.
/// A condition is that clean session connect flag is true, otherwise the connection will be rejected.
/// The client identifier can be a maximum length of 23 characters. If a port is not specified the standard port
/// of 1883 is used. Only web sockets are supported in the browser client.

/// A websocket URL must start with ws:// or wss:// or Dart will throw an exception, consult your websocket MQTT broker
/// for details.
final client = MqttBrowserClient('ws://test.mosquitto.org', '');

Future<int> main() async {
  /// Set logging on if needed, defaults to off
  client.logging(on: false);

  /// Set the correct MQTT protocol for mosquito
  client.setProtocolV311();

  /// If you intend to use a keep alive you must set it here otherwise keep alive will be disabled.
  client.keepAlivePeriod = 20;

  /// The connection timeout period can be set if needed, the default is 5 seconds.
  client.connectTimeoutPeriod = 2000; // milliseconds

  /// The ws port for Mosquitto is 8080, for wss it is 8081
  client.port = 8080;

  /// Add the unsolicited disconnection callback
  client.onDisconnected = onDisconnected;

  /// Add the successful connection callback
  client.onConnected = onConnected;

  /// Add a subscribed callback, there is also an unsubscribed callback if you need it.
  /// You can add these before connection or change them dynamically after connection if
  /// you wish. There is also an onSubscribeFail callback for failed subscriptions, these
  /// can fail either because you have tried to subscribe to an invalid topic or the broker
  /// rejects the subscribe request.
  client.onSubscribed = onSubscribed;

  /// Set a ping received callback if needed, called whenever a ping response(pong) is received
  /// from the broker.
  client.pongCallback = pong;

  /// Set the appropriate websocket headers for your connection/broker.
  /// Mosquito uses the single default header, other brokers may be fine with the
  /// default headers.
  client.websocketProtocols = MqttClientConstants.protocolsSingleDefault;

  /// Create a connection message to use or use the default one. The default one sets the
  /// client identifier, any supplied username/password and clean session,
  /// an example of a specific one below.
  final connMess = MqttConnectMessage()
      .withClientIdentifier('Mqtt_MyClientUniqueId')
      .withWillTopic('willtopic') // If you set this you must set a will message
      .withWillMessage('My Will message')
      .startClean() // Non persistent session for testing
      .withWillQos(MqttQos.atLeastOnce);
  print('EXAMPLE::Mosquitto client connecting....');
  client.connectionMessage = connMess;

  /// Connect the client, any errors here are communicated by raising of the appropriate exception. Note
  /// in some circumstances the broker will just disconnect us, see the spec about this, we however will
  /// never send malformed messages.
  try {
    await client.connect();
  } on Exception catch (e) {
    print('EXAMPLE::client exception - $e');
    client.disconnect();
    return -1;
  }

  /// Check we are connected
  if (client.connectionStatus!.state == MqttConnectionState.connected) {
    print('EXAMPLE::Mosquitto client connected');
  } else {
    /// Use status here rather than state if you also want the broker return code.
    print(
        'EXAMPLE::ERROR Mosquitto client connection failed - disconnecting, status is ${client.connectionStatus}');
    client.disconnect();
    return -1;
  }

  /// Ok, lets try a subscription
  print('EXAMPLE::Subscribing to the test/lol topic');
  const topic = 'test/lol'; // Not a wildcard topic
  client.subscribe(topic, MqttQos.atMostOnce);

  /// The client has a change notifier object(see the Observable class) which we then listen to to get
  /// notifications of published updates to each subscribed topic.
  /// In general you should listen here as soon as possible after connecting, you will not receive any
  /// publish messages until you do this.
  /// Also you must re-listen after disconnecting.
  client.updates!.listen((List<MqttReceivedMessage<MqttMessage?>>? c) {
    final recMess = c![0].payload as MqttPublishMessage;
    final pt =
        MqttPublishPayload.bytesToStringAsString(recMess.payload.message);

    /// The above may seem a little convoluted for users only interested in the
    /// payload, some users however may be interested in the received publish message,
    /// lets not constrain ourselves yet until the package has been in the wild
    /// for a while.
    /// The payload is a byte buffer, this will be specific to the topic
    print(
        'EXAMPLE::Change notification:: topic is <${c[0].topic}>, payload is <-- $pt -->');
    print('');
  });

  /// If needed you can listen for published messages that have completed the publishing
  /// handshake which is Qos dependant. Any message received on this stream has completed its
  /// publishing handshake with the broker.
  client.published!.listen((MqttPublishMessage message) {
    print(
        'EXAMPLE::Published notification:: topic is ${message.variableHeader!.topicName}, with Qos ${message.header!.qos}');
  });

  /// Lets publish to our topic
  /// Use the payload builder rather than a raw buffer
  /// Our known topic to publish to
  const pubTopic = 'Dart/Mqtt_client/testtopic';
  final builder = MqttClientPayloadBuilder();
  builder.addString('Hello from mqtt_client');

  /// Subscribe to it
  print('EXAMPLE::Subscribing to the Dart/Mqtt_client/testtopic topic');
  client.subscribe(pubTopic, MqttQos.exactlyOnce);

  /// Publish it
  print('EXAMPLE::Publishing our topic');
  client.publishMessage(pubTopic, MqttQos.exactlyOnce, builder.payload!);

  /// Ok, we will now sleep a while, in this gap you will see ping request/response
  /// messages being exchanged by the keep alive mechanism.
  print('EXAMPLE::Sleeping....');
  await MqttUtilities.asyncSleep(60);

  /// Finally, unsubscribe and exit gracefully
  print('EXAMPLE::Unsubscribing');
  client.unsubscribe(topic);

  /// Wait for the unsubscribe message from the broker if you wish.
  await MqttUtilities.asyncSleep(2);
  print('EXAMPLE::Disconnecting');
  client.disconnect();
  return 0;
}

/// The subscribed callback
void onSubscribed(String topic) {
  print('EXAMPLE::Subscription confirmed for topic $topic');
}

/// The unsolicited disconnect callback
void onDisconnected() {
  print('EXAMPLE::OnDisconnected client callback - Client disconnection');
  if (client.connectionStatus!.disconnectionOrigin ==
      MqttDisconnectionOrigin.solicited) {
    print('EXAMPLE::OnDisconnected callback is solicited, this is correct');
  }
}

/// The successful connect callback
void onConnected() {
  print(
      'EXAMPLE::OnConnected client callback - Client connection was sucessful');
}

/// Pong callback
void pong() {
  print('EXAMPLE::Ping response client callback invoked');
}