How to send Notification using FCM from one computer to another using Angular2

Question

how can i send notification to one user who login to my site. how can i generate fcmtoken for system or device using angular2,typescript. please help me to solve this.if anyone has any idea so tell me.

 import { Injectable }          from '@angular/core';
import { AngularFireDatabase } from 'angularfire2/database';
import { AngularFireAuth }     from 'angularfire2/auth';
import * as firebase from 'firebase';
import 'rxjs/add/operator/take';
import { BehaviorSubject } from 'rxjs/BehaviorSubject'
import { Observable } from 'rxjs/Observable';
import { Http, Response } from '@angular/http';
import { Headers, RequestOptions } from '@angular/http';

@Injectable()

export class MessagingService {
  messaging = firebase.messaging()
  currentMessage = new BehaviorSubject(null)
  constructor(private db: AngularFireDatabase, private afAuth: AngularFireAuth) { }
  updateToken(token) {
    this.afAuth.authState.take(1).subscribe(user => {
      if (!user) return;
      const data = { [user.uid]: token }
      this.db.object('fcmTokens/').update(data)


    })
  }


  getPermission() {
    this.messaging.requestPermission()
    .then(() => {
      console.log('Notification permission granted.');
      return this.messaging.getToken()
    })
    .then(token => {
      console.log(token)
     // this.updateToken(token)
    })
    .catch((err) => {
      console.log('Unable to get permission to notify.', err);
    });
  }


  receiveMessage() {
    this.messaging.onMessage((payload) => {
     console.log("Message received. ", payload);
     this.currentMessage.next(payload)
   });
 }




}

i am create service MessagingService.ts to the help of this site

https://angularfirebase.com/lessons/send-push-notifications-in-angular-with-firebase-cloud-messaging

but its given error No provider for ConnectionBackend