Angular2/Websocket: how to return an observable for incoming websocket messages

Question

I\'m going to use Angular2 to receive websocket incoming messages and update a webpage based on those received messages. Right now, I\'m using a dummy echo websocket service and

Answer 1

I put it on a plunker and I added a function for sending message to the Websocket endpoint. Here is the important edit:

public GetInstanceStatus(): Observable<any>{
    this.websocket = new WebSocket("ws://echo.websocket.org/"); //dummy echo websocket service
    this.websocket.onopen =  (evt) => {
        this.websocket.send("Hello World");
    };
    return Observable.create(observer=>{
        this.websocket.onmessage = (evt) => { 
            observer.next(evt);
        };
    })
    .share();
}

Update
As you mentioned in your comment, a better alternative way is to use Observable.fromEvent()

websocket = new WebSocket("ws://echo.websocket.org/");
public GetInstanceStatus(): Observable<Event>{
    return Observable.fromEvent(this.websocket,'message');
}

plunker example for Observable.fromEvent();

Also, you can do it using WebSocketSubject, although, it doesn't look like it's ready yet (as of rc.4):

constructor(){
  this.websocket = WebSocketSubject.create("ws://echo.websocket.org/");
}

public sendMessage(text:string){
  let msg = {msg:text};
  this.websocket.next(JSON.stringify(msg));
} 

plunker example

Answer 2

Get onMessage data from socket.

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


@Injectable()

export class HpmaDashboardService {
private socketUrl: any = 'ws://127.0.0.0/util/test/dataserver/ws';
private websocket: any;      

public GetAllInstanceStatus(objStr): Observable<any> {
      this.websocket = new WebSocket(this.socketUrl);
      this.websocket.onopen =  (evt) => {
        this.websocket.send(JSON.stringify(objStr));
      };
      return Observable.create(observer => {
        this.websocket.onmessage = (evt) => {
          observer.next(evt);
        };
      }).map(res => res.data).share();
 }

**Get only single mesage from socket.**

    public GetSingleInstanceStatus(objStr): Observable<any> {
      this.websocket = new WebSocket(this.socketUrl);
      this.websocket.onopen =  (evt) => {
        this.websocket.send(JSON.stringify(objStr));
      };
      return Observable.create(observer => {
        this.websocket.onmessage = (evt) => {
          observer.next(evt);
          this.websocket.close();
        };
      }).map(res => res.data).share();
  }

}