Cancelling accept by signal.

ss.py

import socket
import signal

server = None

def sigusr1_handler(signum, frame):
    server.close()

signal.signal(signal.SIGUSR1, sigusr1_handler)

server = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
server.bind(('', 9999))
server.listen(10)
running = True
while running:
    try:
        conn, addr = server.accept()
        print 'Accepted'
    except Exception:
        running = False
        print 'Cancelled'