[FIXED] Graceful interrupt of EventLoop.sock_accept()

Issue

Consider the following code, how to stop execution in listen()? it seems to hang after sock.close() being called. No exceptions are raised

#!/usr/bin/env python3.5

import asyncio, socket

sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
sock.bind(('localhost', 8080))
sock.listen()
sock.setblocking(0)

async def listen():
    print('listen')
    try:
        while True:
            await asyncio.get_event_loop().sock_accept(sock)
            print('accepted')
    except:
        print('exc')

async def stop():
    await asyncio.sleep(1)
    sock.close()
    print('stopped')


asyncio.ensure_future(listen())
asyncio.ensure_future(stop())
asyncio.get_event_loop().run_forever()

Solution

Closing the socket or removing the file descriptor using loop.remove_reader does not notify loop.sock_accept.

Either cancel it explicitly:

# Listening
accept_future = asyncio.ensure_future(loop.sock_accept(sock))
await accept_future
[...]
# Closing
loop.remove_reader(sock.fileno())
sock.close()
accept_future.cancel()

or use higher-level coroutines such as loop.create_server or asyncio.start_server:

# Using a protocol factory
server = await loop.create_server(protocol_factory, sock=sock) 
# Using callback and streams
server = await asyncio.start_server(callback, sock=sock)

Answered By - Vincent