问rxjs/webSocket -到'ws://localhost:3000/‘的WebSocket连接失败:连接在收到握手响应之前已关闭

EN

connection to 'ws://localhost:3000/' failed: Connection closed before receiving a handshake response

const { app, onServerInitialized } = require('./app');

const port = normalizePort(process.env.PORT);
console.log('Server is running on port ' + process.env.PORT);
app.set('port', port);

const server = http.createServer(app);
onServerInitialized(server);

const app = express();

const onServerInitialized = server => {
    const io = socketio(server);

    io.on('connection', socket => {
        console.log('subscrie');
    });
};

module.exports = { app, onServerInitialized };

import { webSocket, WebSocketSubject } from 'rxjs/webSocket';

export class WebSocketService {
    private ws$: WebSocketSubject<any> = webSocket('ws://localhost:3000');

    public getWSListener() {
        return this.ws$.asObservable().pipe();
    }

    public sendMessage(message: string) {
        this.ws$.next({ message });
    }
}

constructor(
  private webSocketService: WebSocketService,
) {}

ngOnInit() {
  this.webSocketService.getWSListener().subscribe(() => {
    console.log('event')
  });
}