首先声明，这不是我写的，而是我找到的，但是别人写的相当好。

# UDP multicast examples, Hugo Vincent, 2005-05-14.
import socket

def send(data, port=50000, addr='239.192.1.100'):
        """send(data[, port[, addr]]) - multicasts a UDP datagram."""
        # Create the socket
        s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
        # Make the socket multicast-aware, and set TTL.
        s.setsockopt(socket.IPPROTO_IP, socket.IP_MULTICAST_TTL, 20) # Change TTL (=20) to suit
        # Send the data
        s.sendto(data, (addr, port))

def recv(port=50000, addr="239.192.1.100", buf_size=1024):
        """recv([port[, addr[,buf_size]]]) - waits for a datagram and returns the data."""

        # Create the socket
        s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)

        # Set some options to make it multicast-friendly
        s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
        try:
                s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEPORT, 1)
        except AttributeError:
                pass # Some systems don't support SO_REUSEPORT
        s.setsockopt(socket.SOL_IP, socket.IP_MULTICAST_TTL, 20)
        s.setsockopt(socket.SOL_IP, socket.IP_MULTICAST_LOOP, 1)

        # Bind to the port
        s.bind(('', port))

        # Set some more multicast options
        intf = socket.gethostbyname(socket.gethostname())
        s.setsockopt(socket.SOL_IP, socket.IP_MULTICAST_IF, socket.inet_aton(intf) + socket.inet_aton('0.0.0.0'))
        s.setsockopt(socket.SOL_IP, socket.IP_ADD_MEMBERSHIP, socket.inet_aton(addr) + socket.inet_aton('0.0.0.0'))

        # Receive the data, then unregister multicast receive membership, then close the port
        data, sender_addr = s.recvfrom(buf_size)
        s.setsockopt(socket.SOL_IP, socket.IP_DROP_MEMBERSHIP, socket.inet_aton(addr) + socket.inet_aton('0.0.0.0'))
        s.close()
        return data