Websocket连接失败：在建立连接之前关闭WebSocket

Question

我正在使用ngx-remote-desktop软件包连接到外部桌面，  但我一直在控制台中收到错误消息：

与'ws：// localhost：4200 /？ip = 120.18.13.142＆port = 5000＆type = rdp＆image = image / png＆width = 1920＆height = 1080'的WebSocket连接失败：WebSocket在建立连接之前已关闭。

这是我的代码：

@component({
selector: 'app-rdp',
templateUrl: './rdp.component.html',
styleUrls: ['./rdp.component.scss']
})
export class RDPComponent implements OnInit {
private manager: RemoteDesktopManager;
handleHelp() {
console.log('Hello help');
}
handleEnterFullScreen() {
this.manager.setFullScreen(true);
}

 handleExitFullScreen() {
this.manager.setFullScreen(false);
 }

 ngOnInit() {
const tunnel = new WebSocketTunnel('ws://localhost:4200');
this.manager = new RemoteDesktopManager(tunnel);
const parameters = {
    ip: '120.18.13.142',
    port : 5000,
    type: 'rdp',
    image: 'image/png',
    width: window.screen.width,
    height: window.screen.height,
  };     
  this.manager.connect(parameters);
  }
  }

我到底在做错什么？