Elysia websockets and per-event handling

[MinskLeo]

Hi! Great work with Elysia, feels like a promising tool. Everything was great, I was really satisfied with everything that was already implemented, but there is a question about websockets handling. Looks like the only thing which can give Elysia here - just websocket endpoint and no QOL stuff, like something similar to .on() event listeners? I don't have too much experience with websockets, but that's what I'm feeling right now - lack of possibility to easily listen for particular events. Like imagine if I have single endpoint for websocket connection and I would like to have many different events in both directions. Would be good to have some tooling there out of the box, including per-event validation and good type system (as much as it's possible), Eden support for per-event communication.

Is this expected so that developer will implement this event handling system by himself or I missing something in docs? Also talking about docs - looks like Elysia have possibility (app.server.publish(...)) for broadcasting events to all connected clients, but this is not documented.
I would highly appreciate any responses, thanks!

[dy0gu]

I can't seem to find the docs for it either but I'm pretty sure they say somewhere you can indeed do ws.on() for events:

ws.on('open', () => {
	console.log("OPEN")
});
ws.on('close', (event) => {
	console.error("CLOSE: ", event.code)
});
ws.on('error', (event) => {
	console.log("EVENT: ", event)
})

Also, for the most common events like open, close and message Elysia provides callbacks already setup for you: https://elysiajs.com/patterns/websocket#open

Elysia has this documentation problem where some things that expectedly should be together in the docs are not, because technically they come from separate categories.

[MinskLeo]

Hi! Thanks for response. I checked, but ws which passed into handler doesn't have such .on() method. I console logged ws instance and unfortunatelly - there was no .on method too.

And talking about this .on() handlers, I'm thinking about custom events. Something like this:

ws.on('set-device-volume', () => {})
ws.on('add-chat-message', () => {})
ws.on('agent-created', () => {})
// etc.

[dy0gu]

Ah I see what you mean now but no, you can't create custom events on a WebSocket, this is not an Elysia thing it's just how WebSockets work.

The closest thing, and generally the accepted way to do what you want, is to use a message format like [eventname, data_object] then parse it in the message event and run your logic based on the event name.

[MinskLeo]

Ok, got it. But that's what possible from socket.io for example (socket.on() docs). Maybe here planned a bit different approach but feels like socket.io is a lot more "friendly" in such cases and have better developer experience (no need to implement that stuff, it just works out of the box). Anyway, we have what we have. Let's see how Elysia will evolve.

[bmakan]

Socket.io is a library. It's using WebSockets and/or long polling (regular HTTP requests) on the background. But Socket.io != WebSocket.

[MinskLeo]

Socket.io is a library. It's using WebSockets and/or long polling (regular HTTP requests) on the background. But Socket.io != WebSocket.

You right. But I'm not comparing them actually. I'm looking for the same level of socket.io features in the Elysia. But at this moment there is nothing close to that available unfortunately.