ngx-mqtt

ngx-mqtt

This library isn't just a wrapper around MQTT.js for angular >= 2. It uses observables and takes care of subscription handling and message routing.

• Description
• Installation
• Important Note
• Run the Demo Application
• Usage
• Test

Description

ngx-mqtt is well suited for applications with many components and many subscribers. The problem is, if you regulary subscribe to mqtt with client libraries like MQTT.js, still every message is handled with an on-message-eventhandler, so you have to dispatch the received messages for yourself. So, if you have multiple components using mqtt in your code, you just want to only receive the messages for your local filter. Furthermore, if you destroy a component, you want to unsubscribe from mqtt, but only if no other component uses the same filter.

This library exposes a method observe(filter), which returns an Observable. If you subscribe to this observable, the actual mqtt subscription is executed. The topic filter is used to only add matching mqtt messages to the observable. Every other execution of observe(filter) with an already used filter will return the same observable. The observable keeps track of the subscribers and executes an mqtt unsubscribe method, if all subscribers have unsubscribed from the observable.

Installation

Simply install it from npm:

npm install ngx-mqtt --save

Important Note

Since most of the opened issues here are caused by misconfiguration, please make sure your broker listens on websocket and you've configured the right port for it.

mosquitto seems to be the most common broker, so here is an example configuration with websockets.

pid_file /var/run/mosquitto.pid

persistence true
persistence_location /var/lib/mosquitto/

log_dest file /var/log/mosquitto/mosquitto.log

listener 1883

listener 9001 127.0.0.1
protocol websockets

include_dir /etc/mosquitto/conf.d

With this config the broker listens on 1883 for tcp connections and 9001 for websocket connections.

Run the Demo Application

npm run serve:demo # go into demo folder, install npm dependencies and run ng serve

Keep in mind, that the demo is a self contained @angular/cli application, which depends on a ngx-mqtt release and not the source code.

Usage

import { Observable } from 'rxjs/Observable';

import {
  MqttMessage,
  MqttModule,
  MqttService
} from 'ngx-mqtt';

export const MQTT_SERVICE_OPTIONS = {
  hostname: 'localhost',
  port: 9001,
  path: '/mqtt'
};

export function mqttServiceFactory() {
  return new MqttService(MQTT_SERVICE_OPTIONS);
}

@NgModule({
  imports: [
    ...
    MqttModule.forRoot({
      provide: MqttService,
      useFactory: mqttServiceFactory
    })
  ]
  ...
})

export class AppModule { }

@Component({
  template: `
    <h1>{{mesage}}</h1>
    <h1>{{(myOtherMessage$ | async)?.payload.toString()}}</h1>
  `
})
export class ExampleComponent {
  public myOtherMessage$: Observable<MqttMessage>;

  constructor(private _mqttService: MqttService) {
    this._mqttService.observe('my/topic').subscribe((message: MqttMessage) => {
      this.myMessage = message.payload.toString();
    });
    this.myOtherMessage$ = this._mqttService.observe('my/other/topic');
  }

  public unsafePublish(topic: string, message: string): void {
    this._mqttService.unsafePublish(topic, message, {qos: 1, retain: true});
  }
}

For further usage use this module, see demo.module.ts and index.html.

Documentation

npm run docs       # build the documentation
npm run serve:docs # open a local webserver serving the documentation

Test

npm test