python-3.6.zip added from Github

README.cosmo contains the necessary links.

third_party/python/Tools/demo/mcast.py

@@ -0,0 +1,82 @@
+#!/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()