Subprotocols

[davidbrochart]

wsproto seems to support subprotocols, but I'm not sure where to pass them in httpx-ws. Or maybe it's not supported yet?

[frankie567]

Well, there is no dedicated option for that. Actually, subprotocols seem to be declared in a Sec-WebSocket-Protocol protocol header when making the first request. So what you could is to manually set this header:

from httpx_ws import aconnect_ws

async with aconnect_ws("http://localhost:8000/ws", headers={"Sec-WebSocket-Protocol": "sub1, sub2"}) as ws:
    message = await ws.receive_text()
    print(message)
    await ws.send_text("Hello!")

[davidbrochart]

Thanks, that seems to work.
The server is supposed to reply with the selected subprotocol from the list of subprotocols sent by the client. Do you know how to get it?

[frankie567]

Hmm, in the current state, I don't think that's possible. I suppose the client should emit AcceptConnection when opened so we can get that info 🤔

[davidbrochart]

Yes it looks like it, since this event has the accepted subprotocol.
It would be a nice addition to httpx-ws in general, and for me in particular 😄

[frankie567]

Was thinking about this... In terms of API, it would a bit annoying/cumbersome in most cases to have to first handle an AcceptConnection event.

What would you think of this: when opening the connection, we would set the accept event as attribute of WebSocketSession. You can read it if you need, but if you don't care, you don't have to worry about it.

from httpx_ws import aconnect_ws

async with aconnect_ws("http://localhost:8000/ws", subprotocols=["sub1", "sub2"]) as ws:
    print(f"Subprotocol {ws.accept.subprotocol}")
    message = await ws.receive_text()
    print(message)
    await ws.send_text("Hello!")

Or maybe just directly subprotocol, maybe we don't need the event 🤔

from httpx_ws import aconnect_ws

async with aconnect_ws("http://localhost:8000/ws", subprotocols=["sub1", "sub2"]) as ws:
    print(f"Subprotocol {ws.subprotocol}")
    message = await ws.receive_text()
    print(message)
    await ws.send_text("Hello!")

[davidbrochart]

I think ws.subprotocol (without .accept) is shorter and better.