Restructured into several subroutines.

diff --git a/Demo/sockets/mcast.py b/Demo/sockets/mcast.py
index c2bcaef43d9d7943bc5c0785a3a0d58e0260bca2..401138362e9c7567341d65ad36860711e724344d 100755 (executable)
--- a/Demo/sockets/mcast.py
+++ b/Demo/sockets/mcast.py
@@ -14,14 +14,23 @@ import struct
 import regsub
 from socket import *
 from SOCKET import *
-from IN import *                       # Local module, SGI specific!!!
+from IN import *                       # SGI specific!!! (Sorry)
 
-sender = sys.argv[1:]
 
-s = socket(AF_INET, SOCK_DGRAM)
+# Main program
+def main():
+       flags = sys.argv[1:]
+       #
+       if flags:
+               sender(flags[0])
+       else:
+               receiver()
+
 
-if sender:
-       if sys.argv[1] == '-b':
+# Sender subroutine (only one per local area network)
+def sender(flag):
+       s = socket(AF_INET, SOCK_DGRAM)
+       if flag == '-b':
                s.setsockopt(SOL_SOCKET, SO_BROADCAST, 1)
                mygroup = '<broadcast>'
        else:
@@ -33,27 +42,56 @@ if sender:
 ##             data = data + (1400 - len(data)) * '\0'
                s.sendto(data, (mygroup, MYPORT))
                time.sleep(1)
-else:
-       # Allow multiple copies of this program on one machine
-       s.setsockopt(SOL_SOCKET, SO_REUSEPORT, 1) # (Not strictly needed)
 
-       # Bind the socket to my port
-       s.bind('', MYPORT)
 
-       # Construct binary group address from MYGROUP converted to bytes
-       bytes = eval(regsub.gsub('\.', ',', MYGROUP))
+# Receiver subroutine (as many as you like)
+def receiver():
+       # Open and initialize the socket
+       s = openmcastsock(MYGROUP, MYPORT)
+       #
+       # Loop, printing any data we receive
+       while 1:
+               data, sender = s.recvfrom(1500)
+               while data[-1:] == '\0': data = data[:-1] # Strip trailing \0's
+               print sender, ':', `data`
+
+
+# Open a UDP socket, bind it to a port and select a multicast group
+def openmcastsock(group, port):
+       # Import modules used only here
+       import regsub
+       import socket
+       import struct
+       from SOCKET import *
+       from IN import *
+       #
+       # Create a socket
+       s = socket.socket(AF_INET, SOCK_DGRAM)
+       #
+       # Allow multiple copies of this program on one machine
+       # (not strictly needed)
+       s.setsockopt(SOL_SOCKET, SO_REUSEPORT, 1)
+       #
+       # Bind it to the port
+       s.bind('', port)
+       #
+       # Look up multicast group address in name server
+       # (doesn't hurt if it is already in ddd.ddd.ddd.ddd format)
+       group = socket.gethostbyname(group)
+       #
+       # Construct binary group address
+       bytes = eval(regsub.gsub('\.', ',', group))
        grpaddr = 0
        for byte in bytes: grpaddr = (grpaddr << 8) | byte
-
+       #
        # Construct struct mreq from grpaddr and ifaddr
        ifaddr = INADDR_ANY
        mreq = struct.pack('ll', grpaddr, ifaddr)
-
+       #
        # Add group membership
        s.setsockopt(IPPROTO_IP, IP_ADD_MEMBERSHIP, mreq)
+       #
+       return s
 
-       # Loop, printing any data we receive
-       while 1:
-               data, sender = s.recvfrom(1500)
-               while data[-1:] == '\0': data = data[:-1] # Strip trailing \0's
-               print sender, ':', `data`
+
+main()