Restructured into several subroutines.
diff --git a/Demo/sockets/mcast.py b/Demo/sockets/mcast.py
index c2bcaef..4011383 100755
--- a/Demo/sockets/mcast.py
+++ b/Demo/sockets/mcast.py
@@ -14,14 +14,23 @@
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 @@
## 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))
- 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)
-
+# 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
+
+
+main()