import asyncio
import socket
from contextlib import suppress

try:
    import hunter
except ImportError:
    print('Run "pip install hunter" to enable tracing')
else:
    predicates = [hunter.Q(function=func)
                  for func in ('remove_reader', 'add_reader', 'add_writer', 'remove_writer')]
    hunter.trace(hunter.Or(*predicates), kind='call', action=hunter.CallPrinter)


async def main():
    server_sock = socket.socket()
    server_sock.setblocking(False)
    server_sock.bind(('127.0.0.1', 0))
    server_sock.listen()
    sockaddr = server_sock.getsockname()
    with suppress(asyncio.TimeoutError):
        await asyncio.wait_for(loop.sock_accept(server_sock), 0.1)

    print('closing server socket, fd:', server_sock.fileno())
    server_sock.close()

    client_sock = socket.socket()
    client_sock.setblocking(False)
    print('connecting, fd:', client_sock.fileno())
    with suppress(ConnectionRefusedError):
        await loop.sock_connect(client_sock, sockaddr)

loop = asyncio.get_event_loop()
loop.run_until_complete(main())