This error intermittently occurs when I close a server and wait for it to be closed. I seem to get all of the messages I expect in my tests, and my server seems to work fine on windows or linux otherwise, so it's not urgent for me. It seems (to me) that there is no way to catch an exception during accept(). The coroutine is coming directly from windows a overlapped i/o call: (ov = _overlapped.Overlapped(NULL)) Again, this exception only occurs intermittently and usually during my "1K connections tests" and similar load tests. DEBUG:root:waiting.... DEBUG:asyncio:taking long time to close proactor ERROR:asyncio:Task exception was never retrieved future: exception=OSError(22, 'The I/O operation has been aborted because of either a thread exit or an application request', None, 995, None)> Traceback (most recent call last): File "C:\Python36\lib\asyncio\windows_events.py", line 489, in accept_coro yield from future File "C:\Python36\lib\asyncio\proactor_events.py", line 504, in loop conn, addr = f.result() File "C:\Python36\lib\asyncio\windows_events.py", line 702, in _poll value = callback(transferred, key, ov) File "C:\Python36\lib\asyncio\windows_events.py", line 477, in finish_accept ov.getresult() OSError: [WinError 995] The I/O operation has been aborted because of either a thread exit or an application request DEBUG:root:finished.... DEBUG:root:loop dropped out