NotImplementedError on Windows

[Italo Silva]

I tried running the example code on the README, and got this error:

From cffi callback <function _sock_state_cb at 0x00000240DB1BEC10>:
Traceback (most recent call last):
  File "C:\Users\italo\Google Drive\Code\Projects\email-lists\env\lib\site-packages\pycares\__init__.py", line 91, in _sock_state_cb
    sock_state_cb(socket_fd, readable, writable)
  File "C:\Users\italo\Google Drive\Code\Projects\email-lists\env\lib\site-packages\aiodns\__init__.py", line 104, in _sock_state_cb
    self.loop.add_reader(fd, self._handle_event, fd, READ)
  File "C:\Users\italo\AppData\Local\Programs\Python\Python38\lib\asyncio\events.py", line 501, in add_reader
    raise NotImplementedError
NotImplementedError

The program hung after that. After interrupting it, this is the traceback:

Traceback (most recent call last):
  File "a.py", line 11, in <module>
    result = loop.run_until_complete(coro)
  File "C:\Users\italo\AppData\Local\Programs\Python\Python38\lib\asyncio\base_events.py", line 603, in run_until_complete
    self.run_forever()
  File "C:\Users\italo\AppData\Local\Programs\Python\Python38\lib\asyncio\windows_events.py", line 316, in run_forever
    super().run_forever()
  File "C:\Users\italo\AppData\Local\Programs\Python\Python38\lib\asyncio\base_events.py", line 570, in run_forever
    self._run_once()
  File "C:\Users\italo\AppData\Local\Programs\Python\Python38\lib\asyncio\base_events.py", line 1823, in _run_once
    event_list = self._selector.select(timeout)
  File "C:\Users\italo\AppData\Local\Programs\Python\Python38\lib\asyncio\windows_events.py", line 430, in select
    self._poll(timeout)
  File "C:\Users\italo\AppData\Local\Programs\Python\Python38\lib\asyncio\windows_events.py", line 779, in _poll
    status = _overlapped.GetQueuedCompletionStatus(self._iocp, ms)
KeyboardInterrupt

This is on Windows 10 build 2004 with Python 3.8.5 and aiodns 2.0.0.

[P0oOOOo0YA]

Having the same problem on windows. So the workaround would be to run this under WSL.

[Aber]

Same problem in CPython3.9 on windows10.

[Tim R]

Exactly the same problem on Python 3.9.4 on Windows 10 using the example program. Any suggestions?

[Frederic Mariën]

I'm having the same issue.

[BiDuang]

Still got problem on Windows 10 with python3.9.5 and Windows 11 with python 3.10

[Saúl Ibarra Corretgé]

c-ares, what is used underneath, requires a readyness style API, which is not supported on Windows unless you are using a SelectorEventLoop implementation: https://docs.python.org/3/library/asyncio-eventloop.html#asyncio.SelectorEventLoop

[BiDuang]

Okay, thanks. By the way, I made an improvement to let other users know about this issue, and merge it if you think it's good. #105

[Gregor]

In user code, it can be solved by adding

if sys.platform == 'win32':
	asyncio.set_event_loop_policy(asyncio.WindowsSelectorEventLoopPolicy())

Maybe it should be part of the example?

[Saúl Ibarra Corretgé]

Oh that's nice! When did they add to Python?

Happy to take a PR if you're up for it!

[Gregor]

WindowsSelectorEventLoopPolicy was added in 3.7

In 3.8 the default event loop for windows was changed to ProactorEventLoop. At which point this became necessary.

Seems this was already discussed in #78