Demo/sockets/mcast.py

   1 #!/usr/bin/env python
   2 #
   3 # Send/receive UDP multicast packets.
   4 # Requires that your OS kernel supports IP multicast.
   5 #
   6 # Usage:
   7 #   mcast -s (sender, IPv4)
   8 #   mcast -s -6 (sender, IPv6)
   9 #   mcast    (receivers, IPv4)
  10 #   mcast  -6  (receivers, IPv6)
  11
  12 MYPORT = 8123
  13 MYGROUP_4 = '225.0.0.250'
  14 MYGROUP_6 = 'ff15:7079:7468:6f6e:6465:6d6f:6d63:6173'
  15 MYTTL = 1 # Increase to reach other networks
  16
  17 import time
  18 import struct
  19 import socket
  20 import sys
  21
  22 def main():
  23     group = MYGROUP_6 if "-6" in sys.argv[1:] else MYGROUP_4
  24
  25     if "-s" in sys.argv[1:]:
  26         sender(group)
  27     else:
  28         receiver(group)
  29
  30
  31 def sender(group):
  32     addrinfo = socket.getaddrinfo(group, None)[0]
  33
  34     s = socket.socket(addrinfo[0], socket.SOCK_DGRAM)
  35
  36     # Set Time-to-live (optional)
  37     ttl_bin = struct.pack('@i', MYTTL)
  38     if addrinfo[0] == socket.AF_INET: # IPv4
  39         s.setsockopt(socket.IPPROTO_IP, socket.IP_MULTICAST_TTL, ttl_bin)
  40     else:
  41         s.setsockopt(socket.IPPROTO_IPV6, socket.IPV6_MULTICAST_HOPS, ttl_bin)
  42
  43     while True:
  44         data = repr(time.time())
  45         s.sendto(data + '\0', (addrinfo[4][0], MYPORT))
  46         time.sleep(1)
  47
  48
  49 def receiver(group):
  50     # Look up multicast group address in name server and find out IP version
  51     addrinfo = socket.getaddrinfo(group, None)[0]
  52
  53     # Create a socket
  54     s = socket.socket(addrinfo[0], socket.SOCK_DGRAM)
  55
  56     # Allow multiple copies of this program on one machine
  57     # (not strictly needed)
  58     s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
  59
  60     # Bind it to the port
  61     s.bind(('', MYPORT))
  62
  63     group_bin = socket.inet_pton(addrinfo[0], addrinfo[4][0])
  64     # Join group
  65     if addrinfo[0] == socket.AF_INET: # IPv4
  66         mreq = group_bin + struct.pack('=I', socket.INADDR_ANY)
  67         s.setsockopt(socket.IPPROTO_IP, socket.IP_ADD_MEMBERSHIP, mreq)
  68     else:
  69         mreq = group_bin + struct.pack('@I', 0)
  70         s.setsockopt(socket.IPPROTO_IPV6, socket.IPV6_JOIN_GROUP, mreq)
  71
  72     # Loop, printing any data we receive
  73     while True:
  74         data, sender = s.recvfrom(1500)
  75         while data[-1:] == '\0': data = data[:-1] # Strip trailing \0's
  76         print (str(sender) + '  ' + repr(data))
  77
  78
  79 if __name__ == '__main__':
  80     main()