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During an idle moment recently, I wondered if any IP addresses I use might have potentially valid hostnames matching their address. Does that make sense?

Here's an example: the IP address 1.2.3.4 might have the hostname i.ii.iii.iv, but unfortunately the top level domain name .iv doesn't exist.

So, I wrote a script that grabs the list of country-specific TLDs and checks IP addresses you specify to see if any might have hostnames in roman numerals:

#!/usr/bin/perl

use strict;
use warnings;

use LWP::Simple qw(mirror);
use Roman       qw(roman);

use Fatal       qw(open close mirror);

my %ip_to_roman = do {
    my @ip = <DATA>;
    chomp @ip;
    map { $_ => roman_ip($_) } @ip;
};

{
    mirror('http://www.iana.org/cctld/cctld-whois.htm', 'cctld-whois.h
+tm');
    open(my $fh, 'cctld-whois.htm');
    my $page = do { local $/ = undef; <$fh> };
    close $fh;

    while ($page =~ m{>\.(\w\w)(?:&nbsp;|&#150;)*([^<]+)}gms) {
        my ($tld, $country) = ($1, $2);
        $country    =~ s/\s+/ /ms;

        IP: foreach my $address (keys %ip_to_roman) {
            next IP unless $ip_to_roman{$address} =~ m/\.$tld\z/ms;
            print "$address is $ip_to_roman{$address} in $country\n";
        }
    }
}

sub roman_ip {
    my $ip      = shift;
    return join '.', map { roman $_ } split(/\./, $ip);
}

# Put your IP addresses here
__DATA__
1.2.3.4
5.6.7.8
[download]

This script has limitations: it reports some domain names that you can't register. Many TLDs, such as .uk do not allow arbitrary registrations such as foo.uk. Instead, you have to register foo.co.uk, foo.org.uk, etc.

So, what did I find out about my own addresses? I now know I want to register a .ci domain name, but apparently I need to get someone in the Ivory Coast to register this for me and I suspect this may not work as they might only allow .co.ci or .com.ci.

Anyway, it was still a fun experiment.

In reply to IP addresses that might have hostnames in roman numerals by tomhukins

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