services.py 文件源码

def set_ipv4_multicast_source_address(sock, source_address):
    """Sets the given socket up to send multicast from the specified source.

    Ensures the multicast TTL is set to 1, so that packets are not forwarded
    beyond the local link.

    :param sock: An opened IP socket.
    :param source_address: A string representing an IPv4 source address.
    """
    sock.setsockopt(
        socket.IPPROTO_IP, socket.IP_MULTICAST_TTL, 1)
    sock.setsockopt(
        socket.IPPROTO_IP, socket.IP_MULTICAST_IF,
        socket.inet_aton(source_address))