I’m trying to make a component in Angular (18) to subscribe to messages from a vanilla websocket and send messages too.
I have a service that does most of the logic, and I’d like to add an event handler for websocket’s onOpen event.

So far I have this, it works but does not handle the onOpen event from websocket :

component :

import { Subject } from 'rxjs';
...
private messageSubject: Subject<any> = new Subject<any>();

// Connect to the WebSocket server
this.webSocketService.connect(this.device.ipAddress, this.messageSubject);

// Listen for incoming messages
this.messageSubject.asObservable()
.pipe(
  takeUntilDestroyed(this.$destroyRef)
)
.subscribe(
  {
    next: (msg) => console.log('component next', msg),
    error: (error) => console.error('component error', error),
    complete: () => console.log('component complete'),
    // open: () => console.log('component open') I'd like to do this
  }
);

service :

private socket: WebSocket = null;

/** Connect to the WebSocket server */
public connect(host: string, messageSubject: Subject<any>): void {
  if (!this.socket || this.socket.readyState === WebSocket.CLOSED) {
    this.socket = new WebSocket(`ws://${host}:${WebSocketService.PORT}`);

    this.socket.onmessage = (event) => {
      console.log("service message :", event);
      messageSubject.next(event.data);
    };

    this.socket.onclose = () => {
      console.log("service close websocket");
      messageSubject.complete();
    };

    this.socket.onerror = (error) => {
      console.error('oops', error);
      messageSubject.error(error);
    };

    this.socket.onopen = () => {
      console.log('service open')
      // messageSubject.open(); how ?
    }
  }
}

I tried to create subclasses of rxjs’ Subscriber/Subject/Observer/Observable but I couldn’t figure out how or where to put the ‘open’ callback…
How can I achieve this ?

Thank you very much !