doneit-web/src/app/services/chat/websocket.service.ts

import { Injectable } from '@angular/core';
import * as Rx from 'rxjs/Rx';

@Injectable({
  providedIn: 'root'
})
export class WebsocketService {

  constructor() { }

  private subject: Rx.Subject<MessageEvent>;

  public connect(url): Rx.Subject<MessageEvent> {
    if(!this.subject){
      this.subject = this.create(url);
      console.log("Sucessful connect :"+url);
    }
    return this.subject;
  }

  private create(url): Rx.Subject<MessageEvent>{
    let ws = new WebSocket(url);

    let observable = Rx.Observable.create(
      (obs: Rx.Observer<MessageEvent>) => {
        ws.onmessage = obs.next.bind(obs);
        ws.onerror = obs.error.bind(obs);
        ws.onclose = obs.complete.bind(obs);
        return ws.close.bind(ws)
      })

      let observer = {
        next: (data: Object) => {
          if(ws.readyState === WebSocket.OPEN){
            ws.send(JSON.stringify(data));
          }
        }
      }

    return Rx.Subject.create(observer, observable);

  }
}