in reply to unpack blob

I think you data is base64 encoded. Try decoding it first:

use Socket;
my $out = `echo BAABAAXwAACkAAAAAAABLAAAAAAAAAAArBQEKA==|base64 -d`;

print (unpack "H*", $out);
print "\n";
print substr ((unpack "H*", $out), -8);
print "\n";
print inet_ntoa(substr $out, -4);

[download]

and output

VinsWorldcom@C:\Users\VinsWorldcom\tmp> test.pl
0400010005f00000a40000000000012c0000000000000000ac140428
ac140428
172.20.4.40

[download]

Replies are listed 'Best First'.
Re^2: unpack blob
by choroba (Cardinal) on Jan 12, 2016 at 22:33 UTC
    Instead of qx, echo and base64, you can use MIME::Base64 (in core since 5.8) and its decode_base64 function. 
    ($q=q:Sq=~/;[c](.)(.)/;chr(-||-|5+lengthSq)`"S|oS2"`map{chr |+ord
}map{substrSq`S_+|`|}3E|-|`7**2-3:)=~y+S|`+$1,++print+eval$q,q,a,

    [download]
[reply]
[d/l]
[select]

      Obviously a better solution than my backticks and base64 system command. A quick Google turned up Mime::Base64 for base64 in Perl, I did *not* go a step further to see if it was in core and I knew it would not be CPAN module I had downloaded so didn't even try, assumed I didn't have it and rolled something quick.

      Thanks for the tip! Next time I'll check 'corelist' before backtick-ing out.

[reply]
Re^2: unpack blob
by natxo (Scribe) on Jan 12, 2016 at 22:15 UTC
    We got a winner!

    I need to read it a bit more carefully to understand what you just did, but it works ;-)

    Thanks!

[reply]

      Combining all the responses:

      #!perl

use strict;
use warnings;
use Socket;
use MIME::Base64; # in core, thanks choroba

my $blob = "BAABAAXwAACGAAAAAAABLAAAAAAAAAAArBQEKA==";

$blob = decode_base64($blob);

my (
    $dataLength,    # 2 bytes
    $type,          # 2 bytes
    $version,       # 1 byte
    $rank,          # 1 byte
    $flags,         # 2 bytes 
    $serial,        # 4 bytes 
    $ttl,           # 4 bytes 
    $reserved,      # 4 bytes 
    $timestamp,     # 4 bytes
    $data ) = unpack( 'S S C C S L N L L a*', $blob );
# http://www.perlmonks.org/?node_id=1152688 see Tux comment

print $dataLength, "\n";
print "$type\n";
print "$version\n";
print "$rank\n";
print "$flags\n";
print "$serial\n";
print "$ttl\n";
print "$reserved\n";
print "$timestamp\n";
print inet_ntoa($data) . "\n";

      [download]
[reply]
[d/l]

        Side note when using S and L, as you are also using N: The byte order in S and L is architecture dependent. You probably should add the required endianness, like S< or L>. See this overview to see what the difference is.


        Enjoy, Have FUN! H.Merijn
[reply]
[d/l]
[select]

In Section Seekers of Perl Wisdom