https://github.com/python/cpython/commit/0815fe3afc001e4cedc44cc8007ce8597eba7c51
commit: 0815fe3afc001e4cedc44cc8007ce8597eba7c51
branch: main
author: Thomas Grainger <[email protected]>
committer: kumaraditya303 <[email protected]>
date: 2026-10-20T16:48:52+05:30
summary:
gh-156784: do not ignore error port unreachable in proactor event loop
implementation (#156788)
files:
A Misc/NEWS.d/next/Library/2026-09-01-00-00-00.gh-issue-156784.8gvtt4.rst
M Lib/asyncio/windows_events.py
M Lib/test/test_asyncio/test_events.py
M Lib/test/test_asyncio/test_sock_lowlevel.py
diff --git a/Lib/asyncio/windows_events.py b/Lib/asyncio/windows_events.py
index b17ac7ab255fc59..cb00670c006c870 100644
--- a/Lib/asyncio/windows_events.py
+++ b/Lib/asyncio/windows_events.py
@@ -8,7 +8,6 @@
import _overlapped
import _winapi
import errno
-from functools import partial
import math
import msvcrt
import socket
@@ -460,24 +459,20 @@ def finish_socket_func(trans, key, ov):
try:
return ov.getresult()
except OSError as exc:
+ # ERROR_PORT_UNREACHABLE is reported by WSARecvFrom when the
+ # same socket was previously used to send to an address that
+ # isn't listening (gh-91227). Surface it as a
+ # ConnectionResetError, like the other recoverable codes here,
+ # so it propagates to the caller the same way a plain
+ # socket.recvfrom() already does on SelectorEventLoop, instead
+ # of being silently swallowed.
if exc.winerror in (_overlapped.ERROR_NETNAME_DELETED,
- _overlapped.ERROR_OPERATION_ABORTED):
+ _overlapped.ERROR_OPERATION_ABORTED,
+ _overlapped.ERROR_PORT_UNREACHABLE):
raise ConnectionResetError(*exc.args)
else:
raise
- @classmethod
- def _finish_recvfrom(cls, trans, key, ov, *, empty_result):
- try:
- return cls.finish_socket_func(trans, key, ov)
- except OSError as exc:
- # WSARecvFrom will report ERROR_PORT_UNREACHABLE when the same
- # socket is used to send to an address that is not listening.
- if exc.winerror == _overlapped.ERROR_PORT_UNREACHABLE:
- return empty_result, None
- else:
- raise
-
def recv(self, conn, nbytes, flags=0):
self._register_with_iocp(conn)
ov = _overlapped.Overlapped(NULL)
@@ -512,8 +507,7 @@ def recvfrom(self, conn, nbytes, flags=0):
except BrokenPipeError:
return self._result((b'', None))
- return self._register(ov, conn, partial(self._finish_recvfrom,
- empty_result=b''))
+ return self._register(ov, conn, self.finish_socket_func)
def recvfrom_into(self, conn, buf, nbytes=0):
self._register_with_iocp(conn)
@@ -523,8 +517,7 @@ def recvfrom_into(self, conn, buf, nbytes=0):
except BrokenPipeError:
return self._result((0, None))
- return self._register(ov, conn, partial(self._finish_recvfrom,
- empty_result=0))
+ return self._register(ov, conn, self.finish_socket_func)
def sendto(self, conn, buf, flags=0, addr=None):
self._register_with_iocp(conn)
diff --git a/Lib/test/test_asyncio/test_events.py
b/Lib/test/test_asyncio/test_events.py
index 6368f4b04b0fbbb..c59bc64e37df965 100644
--- a/Lib/test/test_asyncio/test_events.py
+++ b/Lib/test/test_asyncio/test_events.py
@@ -1523,9 +1523,18 @@ class Protocol(asyncio.DatagramProtocol):
_received_datagram = None
+ def connection_made(self, transport):
+ self.errors = []
+ self.error_received_event = loop.create_future()
+
def datagram_received(self, data, addr):
self._received_datagram.set_result(data)
+ def error_received(self, exc):
+ self.errors.append(exc)
+ if not self.error_received_event.done():
+ self.error_received_event.set_result(None)
+
async def wait_for_datagram_received(self):
self._received_datagram = loop.create_future()
result = await asyncio.wait_for(self._received_datagram, 10)
@@ -1580,6 +1589,15 @@ def create_socket():
protocol_1.wait_for_datagram_received()
), b'd')
+ if sys.platform == 'win32':
+ # The bad send to addr_3 should be surfaced to the protocol
+ # via error_received() instead of being silently dropped,
+ # while transport_1 keeps working as shown above.
+ loop.run_until_complete(
+ asyncio.wait_for(protocol_1.error_received_event, 10))
+ self.assertTrue(protocol_1.errors)
+ self.assertIsInstance(protocol_1.errors[0], ConnectionResetError)
+
transport_1.close()
transport_2.close()
diff --git a/Lib/test/test_asyncio/test_sock_lowlevel.py
b/Lib/test/test_asyncio/test_sock_lowlevel.py
index c68211968a80d83..723da6488709876 100644
--- a/Lib/test/test_asyncio/test_sock_lowlevel.py
+++ b/Lib/test/test_asyncio/test_sock_lowlevel.py
@@ -613,19 +613,10 @@ def test_create_connection_sock(self):
if sys.platform == 'win32':
- class SelectEventLoopTests(BaseSockTestsMixin,
- test_utils.TestCase):
-
- def create_event_loop(self):
- return asyncio.SelectorEventLoop()
-
-
- class ProactorEventLoopTests(BaseSockTestsMixin,
- test_utils.TestCase):
-
- def create_event_loop(self):
- return asyncio.ProactorEventLoop()
-
+ class _DatagramSendToNonListeningAddressMixin:
+ # Shared by SelectEventLoopTests and ProactorEventLoopTests so that
+ # sock_recvfrom()/sock_recvfrom_into() behave identically on both
+ # event loop implementations.
async def _basetest_datagram_send_to_non_listening_address(self,
recvfrom):
@@ -634,8 +625,9 @@ async def
_basetest_datagram_send_to_non_listening_address(self,
# https://github.com/python/cpython/issues/88906
# https://bugs.python.org/issue47071
# https://bugs.python.org/issue44743
- # The Proactor event loop would fail to receive datagram messages
- # after sending a message to an address that wasn't listening.
+ # Sending a datagram to an address that isn't listening can
+ # surface as a ConnectionResetError on a later receive; the
+ # socket must still be usable afterwards.
def create_socket():
sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
@@ -670,7 +662,8 @@ def create_socket():
# this should send to an address that isn't listening
await self.loop.sock_sendto(socket_1, b'c', addr_3)
- self.assertEqual(await socket_1_recv_task, b'')
+ with self.assertRaises(ConnectionResetError):
+ await socket_1_recv_task
socket_1_recv_task = self.loop.create_task(recvfrom(socket_1))
await asyncio.sleep(0)
@@ -706,6 +699,22 @@ async def recvfrom_into(socket):
self._basetest_datagram_send_to_non_listening_address(
recvfrom_into))
+
+ class SelectEventLoopTests(_DatagramSendToNonListeningAddressMixin,
+ BaseSockTestsMixin,
+ test_utils.TestCase):
+
+ def create_event_loop(self):
+ return asyncio.SelectorEventLoop()
+
+
+ class ProactorEventLoopTests(_DatagramSendToNonListeningAddressMixin,
+ BaseSockTestsMixin,
+ test_utils.TestCase):
+
+ def create_event_loop(self):
+ return asyncio.ProactorEventLoop()
+
else:
import selectors
diff --git
a/Misc/NEWS.d/next/Library/2026-09-01-00-00-00.gh-issue-156784.8gvtt4.rst
b/Misc/NEWS.d/next/Library/2026-09-01-00-00-00.gh-issue-156784.8gvtt4.rst
new file mode 100644
index 000000000000000..699448059114ece
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2026-09-01-00-00-00.gh-issue-156784.8gvtt4.rst
@@ -0,0 +1,3 @@
+:class:`asyncio.ProactorEventLoop` no longer silently ignores
+:exc:`ConnectionResetError` on UDP sockets, matching
+:class:`asyncio.SelectorEventLoop`.
_______________________________________________
Python-checkins mailing list -- [email protected]
To unsubscribe send an email to [email protected]
https://mail.python.org/mailman3//lists/python-checkins.python.org
Member address: [email protected]
