Cannot properly close ws connection in one-sided way.

[truskovskiyk]

Long story short

Cannot properly close ws connection from client side. Full description as code bellow

Expected behaviour

Good patter to close ws connection from the client side in one-sided way.

Actual behaviour

Need to use protected attribute to close ws connection

Steps to reproduce

server.py

import asyncio
import aiohttp.web


async def websocket_handler(request):
    print('Websocket connection starting')
    ws = aiohttp.web.WebSocketResponse()
    await ws.prepare(request)
    print('Websocket connection ready')
    await ws.prepare(request)
    while True:
        if request.transport.is_closing():
            break
        await ws.send_json({'mesasge': 'test'})
        await asyncio.sleep(1)

    return ws


def main():
    loop = asyncio.get_event_loop()
    app = aiohttp.web.Application(loop=loop)
    app.router.add_route('GET', '/ws', websocket_handler)
    aiohttp.web.run_app(app, host='0.0.0.0', port=8080)


if __name__ == '__main__':
    main()

client.py

import asyncio
import aiohttp

URL = f'http://0.0.0.0:8080/ws'


async def main():
    session = aiohttp.ClientSession()
    count = 0
    max_query = 2
    async with session.ws_connect(URL) as ws:
        while True:
            msg = await ws.receive_json()
            print(f"get from the server {msg}")
            count += 1
            if count > max_query:
                proto = ws._writer.protocol
                proto.transport.close()
                break


if __name__ == '__main__':
    loop = asyncio.get_event_loop()
    loop.run_until_complete(main())

python server.py
python client.py

Your environment

macOS Mojave 10.14
python3.6.1
aiohttp==3.5.0a1

[aio-libs-bot]

GitMate.io thinks the contributor most likely able to help you is @asvetlov.

Possibly related issues are #1814 (Close websocket connection when pong not received), #3052 (SSL with closed connections), #523 (Not all connections are closed (pending: 0)), #253 (Connection not closed when request is cancelled), and #15 (No way to close a response on a timeout).

[serhiy-storchaka]

You need to run a separate task to listen the WebSocket and handle the closing handshake.

server.py:

import asyncio
import aiohttp.web


async def websocket_handler(request):
    print('Websocket connection starting')
    ws = aiohttp.web.WebSocketResponse(heartbeat=1)
    await ws.prepare(request)
    print('Websocket connection ready')

    async def _ws_listener() -> None:
        async for msg in ws:  # handles ping-pong and closing internally
            # What to do with unexpected messages?
            # It depends on you.
            pass

    reader = asyncio.create_task(_ws_listener())
    while not ws.closed:
        await ws.send_json({'mesasge': 'test'})
        await asyncio.sleep(1)
    await reader

    return ws


def main():
    app = aiohttp.web.Application()
    app.router.add_route('GET', '/ws', websocket_handler)
    aiohttp.web.run_app(app, host='0.0.0.0', port=8080)


if __name__ == '__main__':
    main()

client.py:

import asyncio
import aiohttp

URL = f'http://0.0.0.0:8080/ws'


async def main():
  session = aiohttp.ClientSession()
  async with session:
    count = 0
    max_query = 2
    async with session.ws_connect(URL) as ws:
        while True:
            msg = await ws.receive_json()
            print(f"get from the server {msg}")
            count += 1
            if count > max_query:
                break


if __name__ == '__main__':
    asyncio.run(main())

[Dreamsorcerer]

I think this is by design and just following the websocket standard:

The underlying TCP connection, in most normal cases, SHOULD be closed first by the server
https://www.rfc-editor.org/rfc/rfc6455#section-7.1.1

i.e. As part of your websocket API, there should be a close command you can send to the server, at which point the server can initiate closing of the connection.