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#!/usr/bin/env python3
"""
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
import time
import struct
import socket
import sys
def main():
group = MYGROUP_6 if "-6" in sys.argv[1:] else MYGROUP_4
if "-s" in sys.argv[1:]:
sender(group)
else:
receiver(group)
def sender(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)
if addrinfo[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)
while True:
data = repr(time.time()).encode('utf-8') + b'\0'
s.sendto(data, (addrinfo[4][0], MYPORT))
time.sleep(1)
def receiver(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
if addrinfo[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
while True:
data, sender = s.recvfrom(1500)
while data[-1:] == '\0': data = data[:-1] # Strip trailing \0's
print(str(sender) + ' ' + repr(data))
if __name__ == '__main__':
main()
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