Manually upgrading upgrade requests to socket.io socket?

[Blakeinstein]

I am trying to manually handle the socket upgrade request, so that I can proxy to another port on subdomains, and go to socket.io otherwise. Trying to use http2-proxy, but I cant find documentation on how to upgrade to socket.io socket

server.on('upgrade', (req, socket, head) => {
  if (req.headers.host ...)
    return proxy.ws(req, socket, head, { target ... });
  io.????? // upgrade to socket.io here
}

I also tried

io.use((socket, next) => {
  if (socket.request.headers.host ...)
    return ??? // Proxy to target port here
  next();
}

And I am confused as to what I should do to proxy socket.io socket

[darrachequesne]

You can manually upgrade with io.engine.handleUpgrade().

Please see the documentation here: https://socket.io/docs/v4/server-api/#engine-handleUpgrade-request-socket-head

[Blakeinstein]

Thanks! BTW Why is io.engine of type any?

[Blakeinstein]

You can manually upgrade with io.engine.handleUpgrade().
Please see the documentation here: socket.io/docs/v4/server-api/#engine-handleUpgrade-request-socket-head

I am unsure why you put in the effort of copying the solution post as is, and then replying back. Maybe I am missing some key information you wanted to add on here?