Maybe BUG? The wsproto backend didn't raise exception for unexpected client disconnection, however websockets do.

[WSH032]

When the client disconnects without sending a close frame, Starlette is unable to perceive it, even if websocket.send_text has already been called.

• This situation occurs only when using the wsproto backend,
• for webSockets, it raises an exception.

It is a bit similar to starlette/issues/759, but maybe more unsettling,

because it's a reasonable functionality for the server to only send messages to the client without receiving any from the client.
However, the client can use this bug to infinitely create isolated asynchronous tasks, consuming server resources.

---

To reproduce this issue:

Server

# test_server.py
import asyncio
from itertools import count

from fastapi import FastAPI
from starlette.websockets import WebSocket

app = FastAPI()


@app.websocket_route("/")
async def _(websocket: WebSocket):

    print(websocket.client.host, websocket.client.port)
    await websocket.accept()
    for i in count():
        await websocket.send_text("1")
        print(i)
        print("client     ", websocket.client_state)
        print("application", websocket.application_state)
        await asyncio.sleep(1)

client connect ws and suddenly shutdown

import sys
import time
from contextlib import ExitStack

import httpx
from httpx_ws import connect_ws


def main():
    # establish a websocket connection
    stack = ExitStack()
    client = httpx.Client()
    ws = stack.enter_context(connect_ws("ws://localhost:8000/", client))

    # suddenly shut down the client
    time.sleep(2)
    sys.exit(0)


if __name__ == "__main__":
    main()

Then, launch wsproto

uvicorn test_server:app --ws wsproto --ws-ping-interval 1 --ws-ping-interval 1

you will get infinite:

1
client      WebSocketState.CONNECTED
application WebSocketState.CONNECTED

...

248
client      WebSocketState.CONNECTED
application WebSocketState.CONNECTED

If websockets, it will be good:

uvicorn test_server:app --ws websockets --ws-ping-interval 1 --ws-ping-interval 1

websockets.exceptions.ConnectionClosedError: no close frame received or sent
INFO:     connection closed