wsocket.ts

import { Injectable } from '@angular/core';

import { ConnectableObservable, Observable, Observer, Subject, ReplaySubject } from 'rxjs';


@Injectable()
export class WSocketService {
    constructor() {}
    private msocket: Subject<MessageEvent>;

    public connect(url) : Subject<MessageEvent> {
        if (!this.msocket) {
            this.msocket = this.create(url)
        }
        return this.msocket;
    }

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

        let observable = Observable.create(
            (obs: 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: JSON) => {
                if (ws.readyState === WebSocket.OPEN) {
                    ws.send(JSON.stringify(data));
                }
            },
        };
        return Subject.create(observer, observable);
    }
}