Description

assignee = None
closed_at = None
created_at = <Date 2022-03-20.14:58:17.671>
labels = ['3.10', 'OS-windows', 'expert-asyncio']
title = "asyncio proactor udp transport stops responding after send to port that isn't listening"
updated_at = <Date 2022-03-20.15:48:54.679>
user = 'https://github.com/esoma'

activity = <Date 2022-03-20.15:48:54.679>
actor = 'esoma'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Windows', 'asyncio']
creation = <Date 2022-03-20.14:58:17.671>
creator = 'esoma'
dependencies = []
files = ['50691', '50692']
hgrepos = []
issue_num = 47071
keywords = ['patch']
message_count = 4.0
messages = ['415611', '415612', '415614', '415617']
nosy_count = 7.0
nosy_names = ['paul.moore', 'tim.golden', 'asvetlov', 'zach.ware', 'yselivanov', 'steve.dower', 'esoma']
pr_nums = ['32011']
priority = 'normal'
resolution = None
stage = 'patch review'
status = 'open'
superseder = None
type = None
url = 'https://bugs.python.org/issue47071'
versions = ['Python 3.10']

Activity

1. esoma commented on Mar 20, 2022

   

   esomamannequin

   on Mar 20, 2022

   MannequinAuthor

   More actions

   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.

   Reacted by R.
2. esoma

   added

   3.10 (EOL)end of lifeend of life

   OS-windows

   topic-asyncio

   on Mar 20, 2022
3. esoma commented on Mar 20, 2022

   

   esomamannequin

   on Mar 20, 2022

   MannequinAuthor

   More actions

   Uploading my hack to asyncio.windows_events.py -- this is based off 3.10.2's distribution.
4. asvetlov commented on Mar 20, 2022

   

   asvetlov

   on Mar 20, 2022

   Contributor

   More actions

   Thanks for the report.
   Could you make a pull request?
   The whole attached windows_events.py is hard to analyze.
5. esoma commented on Mar 20, 2022

   

   esomamannequin

   on Mar 20, 2022

   MannequinAuthor

   More actions

   Certainly: #32011
6. ezio-melotti

   transferred this issue fromon Apr 10, 2022
7. ezio-melotti

   added this to asyncioon Jun 20, 2022
8. ezio-melotti

   moved this to Todo in asyncioon Jul 17, 2022
9. msoxzw commented on Jul 26, 2022

   

   msoxzw

   on Jul 26, 2022

   Contributor

   More actions

   As far as I know, there are several alternative solutions from open source projects:
   The Go programming language - https://github.com/golang/go/blob/ceefd3a37bb2a77b1e9a76fc74360c68ef16ddb8/src/internal/poll/fd_windows.go#L341-L352
   The libuv - https://github.com/libuv/libuv/blob/6c692ad1cbcc5083ec90954a4b091b660aedfc10/src/win/udp.c#L462-L486
10. esoma commented on Jul 26, 2022

    

    esoma

    on Jul 26, 2022

    SponsorContributorAuthor

    More actions

    Looks like the libuv solution is similar to my PR -- just trying again.

    The go solution is much simpler though. I'll try that out.
11. 12 remaining items

12. jaycelq commented on Aug 24, 2023

    

    jaycelq

    on Aug 24, 2023

    More actions

    Any update on this issue?

    Reacted by Giovanni, Mikhail Razgovorov, synodriver, baterflyrity and Thomas Grainger
13. gvanrossum

    added a commit that references this issue on Mar 23, 2024

    gh-91227: Ignore ERROR_PORT_UNREACHABLE in proactor recvfrom() (#32011)

    f11d0d8
14. gvanrossum

    closed this as completedon Mar 23, 2024
15. github-project-automation

    moved this from Todo to Done in asyncioon Mar 23, 2024
16. miss-islington

    added a commit that references this issue on Mar 25, 2024

    pythongh-91227: Ignore ERROR_PORT_UNREACHABLE in proactor recvfrom() (p…

    88e75de
17. serhiy-storchaka

    added 3 commits that reference this issue on Mar 25, 2024

    [3.11] pythongh-91227: Ignore ERROR_PORT_UNREACHABLE in proactor recv…

    f9d904c

    [3.12] gh-91227: Ignore ERROR_PORT_UNREACHABLE in proactor recvfrom() (…

    bd2c60f

    [3.11] gh-91227: Ignore ERROR_PORT_UNREACHABLE in proactor recvfrom() (…

    6261322
18. adorilson

    added a commit that references this issue on Mar 25, 2024

    pythongh-91227: Ignore ERROR_PORT_UNREACHABLE in proactor recvfrom() (p…

    1887240
19. NGRsoftlab

    added 2 commits that reference this issue on Apr 2, 2024

    Squashed commit of the following:

    1b5fe4c

    Squashed commit of the following:

    a016a54
20. diegorusso

    added a commit that references this issue on Apr 17, 2024

    pythongh-91227: Ignore ERROR_PORT_UNREACHABLE in proactor recvfrom() (p…

    076919f
21. wcoldren

    added 2 commits that reference this issue on Jun 17, 2026

    New Game: Zillion (ArchipelagoMW#1081)

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    Zillion: map tracker in client (ArchipelagoMW#1136)

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22. graingert

    added a commit that references this issue on Aug 31, 2026

    pythongh-127057: Re-arm proactor datagram read loop after a recoverab…

    3c2e804

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