mcast.py

#!/usr/bin/env python
#
# Send/receive UDP multicast packets.
# Requires that your OS kernel supports IP multicast.
#
# Usage:
# mcast -s (sender, IPv4)
# mcast -s -6 (sender, IPv6)
# mcast (receivers, IPv4)
# mcast -6 (receivers, IPv6)

MYPORT=8123
MYGROUP_4='225.0.0.250'
MYGROUP_6='ff15:7079:7468:6f6e:6465:6d6f:6d63:6173'
MYTTL=1# Increase to reach other networks

importtime
importstruct
importsocket
importsys

defmain():
group=MYGROUP_6if"-6"insys.argv[1:] elseMYGROUP_4

if"-s"insys.argv[1:]:
sender(group)
else:
receiver(group)


defsender(group):
addrinfo=socket.getaddrinfo(group, None)[0]

s=socket.socket(addrinfo[0], socket.SOCK_DGRAM)

# Set Time-to-live (optional)
ttl_bin=struct.pack('@i', MYTTL)
ifaddrinfo[0] ==socket.AF_INET: # IPv4
s.setsockopt(socket.IPPROTO_IP, socket.IP_MULTICAST_TTL, ttl_bin)
else:
s.setsockopt(socket.IPPROTO_IPV6, socket.IPV6_MULTICAST_HOPS, ttl_bin)

whileTrue:
data=repr(time.time())
s.sendto(data+'\0', (addrinfo[4][0], MYPORT))
time.sleep(1)


defreceiver(group):
# Look up multicast group address in name server and find out IP version
addrinfo=socket.getaddrinfo(group, None)[0]

# Create a socket
s=socket.socket(addrinfo[0], socket.SOCK_DGRAM)

# Allow multiple copies of this program on one machine
# (not strictly needed)
s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)

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

group_bin=socket.inet_pton(addrinfo[0], addrinfo[4][0])
# Join group
ifaddrinfo[0] ==socket.AF_INET: # IPv4
mreq=group_bin+struct.pack('=I', socket.INADDR_ANY)
s.setsockopt(socket.IPPROTO_IP, socket.IP_ADD_MEMBERSHIP, mreq)
else:
mreq=group_bin+struct.pack('@I', 0)
s.setsockopt(socket.IPPROTO_IPV6, socket.IPV6_JOIN_GROUP, mreq)

# Loop, printing any data we receive
whileTrue:
data, sender=s.recvfrom(1500)
whiledata[-1:] =='\0': data=data[:-1] # Strip trailing \0's
print (str(sender) +' '+repr(data))


if__name__=='__main__':
main()