SPUG: DNS Lookups

[Martin, Asa]

Here's something I've been wondering about for a while. Why is gethostbyname not able to resolve many addresses, when my nslookup program (on both my Solaris 2.8 box and Windows 2000) can? For example, I often have to write scripts that convert between IP addresses and DNS names. Currently I just run calls to nslookup and parse the results. I don't like that method because it's not very platform independent. I found this script in the book "Network Programming with Perl":

#!/usr/local/bin/perl
# file: ip_trans.pl
use Socket;
my $ADDR_PAT = '^\d+\.\d+\.\d+\.\d+$';
while (<>) {
    chomp;
    die "$_: Not a valid address" unless /$ADDR_PAT/o;
    my $name = gethostbyaddr(inet_aton($_),AF_NET);
    $name ||= '?';
    print "$_ => $name\n";
}

However, this script does not resolve many addresses. For example the following list comes back with '?'

205.188.208.137
152.163.188.39
64.12.96.198
205.188.209.75
152.163.189.103
152.163.189.72
152.163.188.8
205.188.208.167
207.172.11.233
205.188.209.13
205.188.208.74
205.188.208.75
152.163.188.168
198.81.23.78
205.188.209.170
205.188.209.171

Do I need to do something on my box to get the perl functions to work? Or is nslookup doing something else that can't be done with perl.

Thanks,

Asa Martin


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