python udp broadcast

broadcast.py

import atexit
import fcntl
import socket
import struct
import time
import traceback

INTERVAL = 5
sockets = {}

def get_ip_by_name(interface):
    s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
    try:
        return socket.inet_ntoa(fcntl.ioctl(
            s.fileno(),
            0x8915,  # SIOCGIFADDR
            struct.pack('256s', interface[:15].encode('utf-8'))
        )[20:24])
    except OSError:
        pass


def get_all_ip():
    ips = []
    for _, name in socket.if_nameindex():
        try:
            ip = get_ip_by_name(name)
        except OSError:
            continue
        if ip:
            ips.append(ip)

    return ips


def update_sockets():
    global sockets
    ip_set = set(get_all_ip())
    for ip in sockets:
        if ip not in ip_set:
            sockets.pop(ip).close()
    for ip in ip_set:
        if ip not in sockets:
            sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
            sock.setsockopt(socket.SOL_SOCKET, socket.SO_BROADCAST, 1)
            sock.bind((ip, 0))
            sockets[ip] = sock


def close_sockets():
    global sockets
    for sock in sockets.values():
        sock.close()


atexit.register(close_sockets)


def broadcast():
    global sockets
    while True:
        start = time.time()
        update_sockets()
        for sock in sockets.values():
            sock.sendto(b'abc', ('<broadcast>', 12345))
        delay = start + INTERVAL - time.time()
        if delay > 0:
            time.sleep(delay)


if __name__ == '__main__':
    while True:
        try:
            broadcast()
        except KeyboardInterrupt:
            break
        except:
            traceback.print_exc()
        time.sleep(10)