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

Anonymous Monk has asked for the wisdom of the Perl Monks concerning the following question:

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";
[download]

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

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

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Re: Values of Multicast Socket Options on Solaris 10 are not returned by getsockopt. by zwon (Abbot) on Nov 04, 2012 at 11:43 UTC
Note, that getsockopt returns packed value. Try `print "ttl => " . unpack("L", $ttl) . "\n";` [download] instead. Also, when you're setting socket option you should pack its value.	[reply] [d/l]
Re^2: Values of Multicast Socket Options on Solaris 10 are not returned by getsockopt. by Anonymous Monk on Nov 04, 2012 at 11:55 UTC
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.	[reply]