Socket.IO on Subdomain vhost and proxy

I'm trying to proxy socket.example.com:4000 to a websocket server mydomain.com:3000 but the client can also connect to the server through *.example.com:4000, It's like vhost has no effect and the proxy configuration is set globally. I don't want other subdomains be proxied.

i use vhost and http-proxy-middleware

const options = {
    target: 'http://example.com:3000',
    changeOrigin: true,
    ws: true
};
    
const wsProxy = createProxyMiddleware(options);

app.use(vhost('socket.example.com', wsProxy));

I didn't need vhost nor http-proxy-middleware. i used http-proxy and some vanilla javascript.

import httpProxy from 'http-proxy';

const proxy = httpProxy.createProxyServer({
    target: {
        host: 'example.com',
        port: 4001
    }
});

server.on('upgrade', (req, socket, head) => {
    const domain = req.headers.host;
    const host = domain.split(':')[0];

    if (host === 'socket.example.com') {
        proxy.ws(req, socket, head);
    } else {
        socket.destroy();
    }
});

##Update## Running on the same server without proxy or dedicated websocket server.

import { Server } from "socket.io";

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

const io = new Server(server, {
    allowRequest: (req, fn) => {
        const domain = req.headers.host;
        const host = domain.split(':')[0];

        fn(null, host === `socket.example.com`);
    }
});

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