udp.py 文件源码

def get_multicast_socket(sock=None):
    if not sock:
        sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)

    sock.settimeout(0.001)

    # set multicast interface to any local interface
    sock.setsockopt(socket.IPPROTO_IP, socket.IP_MULTICAST_IF, socket.inet_aton('0.0.0.0'))

    # Enable multicast, TTL should be <32 (local network)
    sock.setsockopt(socket.IPPROTO_IP, socket.IP_MULTICAST_TTL, 5)

    # Allow reuse of addresses
    sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)

    # Allow receiving multicast broadcasts (subscribe to multicast group)
    try:
        mreq = struct.pack('4sL', socket.inet_aton(multicast_ip), socket.INADDR_ANY)
        sock.setsockopt(socket.IPPROTO_IP, socket.IP_ADD_MEMBERSHIP, mreq)

        # Do not loop back own messages
        sock.setsockopt(socket.SOL_IP, socket.IP_MULTICAST_LOOP, 0)
    except OSError as e:
        logger.error('Unable to obtain socket with multicast enabled.')
        raise e

    port = None
    for i in range(30100, 30105):
        try:
            # Binding to 0.0.0.0 results in multiple messages if there is multiple interfaces available
            # Kept as-is to avoid losing messages
            sock.bind(('0.0.0.0', i))
            port = i
            break
        except OSError as e:
            # Socket already in use without SO_REUSEADDR enabled
            continue

    if not port:
        raise RuntimeError('No IMC multicast ports free on local interface.')

    return sock