log sent and received messages

client6.py

 import argparse
+import logging
 import socket
 import struct
-import sys
 
 if not hasattr(socket, 'SO_BINDTODEVICE'):
     socket.SO_BINDTODEVICE = 25
 
+hostname = socket.gethostname()
+logging.basicConfig(filename=hostname+'-client6.log', encoding='utf-8', format='%(asctime)s %(message)s', level=logging.DEBUG)
+
 parser = argparse.ArgumentParser()
 parser.add_argument("multicast_group", help="Multicast IPv6 to use for subscription")
 
@@ -16,16 +19,17 @@ sock = socket.socket(socket.AF_INET6, socket.SOCK_DGRAM)
 sock.bind(server_address)
 
 # on all interfaces.
-for ifidx, ifname in socket.socket.if_nameindex():
-    print("joining %s @ [%d]%s" % (args.multicast_group, ifidx, ifname))
+for ifidx, ifname in socket.if_nameindex():
+    if ifname in ('lo', 'can0'):
+        continue
+    logging.info('%s joining %s @ [%d]%s', hostname, args.multicast_group, ifidx, ifname)
     bifidx = struct.pack("@i", ifidx)
-    mreq = socket.inet_pton(socket.AF_INET6, args.multicast_group) + \
-            bifidx
-    sock.setsockopt(socket.IPPROTO_IPV6, socket.IPV6_JOIN_GROUP, mreq)  # = IPV6_ADD_MEMBERSHIP
+    mreq = socket.inet_pton(socket.AF_INET6, args.multicast_group) + bifidx
+    sock.setsockopt(socket.IPPROTO_IPV6, socket.IPV6_JOIN_GROUP, mreq)
 
 try:
     while True:
         data, address = sock.recvfrom(10240)
-        print(data.decode("utf-8"))
+        logging.info('%s received %s', hostname, data.decode("utf-8"))
 finally:
     sock.close()

server6.py

 import argparse
+import logging
 import socket
-import struct
 import traceback
 
+hostname = socket.gethostname()
+logging.basicConfig(filename=hostname+'-server6.log', encoding='utf-8', format='%(asctime)s %(message)s', level=logging.DEBUG)
+
 parser = argparse.ArgumentParser()
 parser.add_argument("addr", help="IPv6 address to use for source")
 parser.add_argument("multicast_group", help="Multicast IPv6 address to use for destination")
 
 args = parser.parse_args()
-print(args.addr)
-print(args.multicast_group)
+logging.info('host %s will send to %s with source address %s', hostname, args.multicast_group, args.addr)
 
 ttl = 12
 sock = socket.socket(socket.AF_INET6, socket.SOCK_DGRAM)
@@ -21,6 +23,7 @@ try:
         input_msg = input('msg --> ')
         try:
             sock.sendto(input_msg.encode("utf-8"), (args.multicast_group, 10000))
+            logging.info('%s sent %s', hostname, input_msg)
         except Exception:
             traceback.print_exc()
             continue