Using PHP classes to navigate distributed whois databases - Overview of the whois landscape (
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Excepting for the moment .com/.net/.org, most TLD's have a whois
server somewhere listening on port 43 where you can connect to
it, give it a domain name, and get a record back for that domain
name if it exists. The formats of the returned record vary across
different servers.
The .com/.net/.org namespace is a little more convoluted. We have the
central registry database at whois.nsiregistry.net which contains a
minimal record for all domains in this namespace, and then each
registrar operates it's own whois server with more complete records
for only the domains they administer. Further, each registrar has it's
own whois output format for their own records.
The result of all this is One Big Mess. Depending on whether you want
to look up a ccTLD or a gTLD (generic TLD), and if the latter, who
the registrar is and where their whois server is; trying to create
a script to integrate this kind of functionality into your website
can be, in a word, nightmarish.
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