Values of Multicast Socket Options on Solaris 10 are not returned by getsockopt.

[Anonymous Monk]

I want to query (and set) the multicast TTL and loopback values using getsockopt (setsockopt). no errors occur, but no values are returned either. i can't use CPAN IO::Socket::Multicast due to configuration management restrictions.

use Socket;
require "netinet/in.ph";
my $s;
socket($s, PF_INET, SOCK_DGRAM, getprotobyname('udp')) or  die;
my $ttl = getsockopt($s, getprotobyname('ip'), IP_MULTICAST_TTL()) or 
+die;
print "ttl => $ttl\n";

results are "ttl =>". same thing happens with IP_MULTICAST_LOOP. and as expected, since i can't query the value, setsockopt also fails.

i am running perl version 5.8.4 on solaris 10. this is the standard package delivered with solaris 10 installation disks and has not been altered.

i ran "perl -V" and the results included "usesocks=undef" but the libraries included "-libs=-lsocket" and "perllibs=-lsocket". perhaps this is related?

thank you for any advice you can give me

[zwon]

Note, that getsockopt returns packed value. Try

print "ttl => " . unpack("L", $ttl) . "\n";

instead. Also, when you're setting socket option you should pack its value.

[Anonymous Monk]

thank-you.

i came across the same solution. note that the TTL and LOOP multicast options are 1 byte long, so i had to do $ttl = unpack('C', $ttl).

i had similar problems using IO::Socket (V1.28) and found that the unpack done in it assumed integer values when unpacking. it also did not do packing when setting values.

in summary, i was trying to implement the IO::Socket::Multicast module as described in Network Programming with Perl by Lincoln D. Stein, 2001, found in chapter 21, page 620. but none of the examples would work. so i stepped back and tried implementing using the basic Socket module.

now that i have this step working, i hope to make more progress.