#How to find the multicast address on Windows:
#C:\> netsh interface ip show joins
#on Linux:
#$ ip maddr show

import socket
import struct
import sys

PORT=10000
multicast_group = '224.3.29.71'
server_address = ('', PORT)

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

# Bind to the server address
sock.bind(server_address)


# Tell the operating system to add the socket to the multicast group
# on all interfaces.
group = socket.inet_aton(multicast_group)
mreq = struct.pack('4sL', group, socket.INADDR_ANY)
sock.setsockopt(socket.IPPROTO_IP, socket.IP_ADD_MEMBERSHIP, mreq)

# Receive/respond loop
while True:
    print ('\nwaiting to receive message on ',multicast_group, PORT)
    
    data, address = sock.recvfrom(1024)
    
    print('received %s bytes from %s' % (len(data), address))
    print(data)

    print ('sending acknowledgement to', address)
    sock.sendto(data, address)