Server Disconnect Handling Clarification

[duckboy81]

Hello there,

I've got a concern about being able to immediately and forcibly disconnect a rogue client (one that doesn't care about WS standards and packets sent to it -- merely wants to tie up server resources. DOS maybe?).

It seems to me that even if I grab the socket myself and try to close it by calling my_async_server._get_socket(sid).close(wait=False, abort=True), the call is passed to the asgi handler and the socket is not actually disconnected immediately.

Further, looking at the wireshark captures, it seems any message I send after that "disconnect" attempt are still ACK'd at a socket level until about 30s later when the connection finally closes with a FIN ACK (which I can only imagine is the failsafe disconnect from the ping/pongs failing)

I believe the issue stems from this writer loop not breaking until the queue is empty, though this is reaching the limit of my research. Seems like there should be a way to jump to ws.close() immediately.

python-engineio/src/engineio/async_socket.py

Lines 192 to 207 in 6650be6

	async def writer():
	while True:
	packets = None
	try:
	packets = await self.poll()
	except exceptions.QueueEmpty:
	break
	if not packets:
	# empty packet list returned -> connection closed
	break
	try:
	for pkt in packets:
	await ws.send(pkt.encode())
	except:
	break
	await ws.close()

Thanks!

[duckboy81]

This is a non-issue. I was emitting a connect_error event on the server side just prior to disconnecting the client in order to convince the frontend to reconnect gracefully, but that seems to have messed up the internals and prevented the disconnect.