New submission from Erik Soma <stillusing...@gmail.com>:
Reproducer attached. Change `USE_PROACTOR` to `False` to use the `SelectorEventLoop` instead, which doesn't exhibit this behavior. The output on my machine when using the proactor loop is: ``` datagram received b'ping 1' datagram received b'ping 2' ``` And the selector loop (which is the behavior I would expect): ``` datagram received b'ping 1' datagram received b'ping 2' datagram received b'ping 3' ``` At a high level, after sending data to an address that isn't listening the asyncio protocol will no longer receive messages. Digging deeper, `_ProactorDatagramTransport._loop_reading` encounters the windows error 1234 (ERROR_PORT_UNREACHABLE) after the "bad send". It appears this a (undocumented/buggy?) behavior of `WSARecvFrom` where the next call to it after an unreachable `WSASendTo` in UDP mode will return the ICMP unreachable message. The actual error is returned from `GetOverlappedResult`. I've hacked together a fix that retries `IocpProactor.recvfrom` if the result is ERROR_PORT_UNREACHABLE. It fixes the issue for the reproducer and my actual use case, but it's probably not ideal. My solution for the moment is just to use the SelectorEventLoop instead. ---------- components: Windows, asyncio files: udpbug2.py messages: 415611 nosy: asvetlov, esoma, paul.moore, steve.dower, tim.golden, yselivanov, zach.ware priority: normal severity: normal status: open title: asyncio proactor udp transport stops responding after send to port that isn't listening versions: Python 3.10 Added file: https://bugs.python.org/file50691/udpbug2.py _______________________________________ Python tracker <rep...@bugs.python.org> <https://bugs.python.org/issue47071> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
