In this article we are going to create a whois lookup client application. The main aim of this application will be to look up information about websites on various known WHOIS servers.
Information about websites such as the owner's name, address, domain name, and so on are stored on databases guided by the RFC 954 protocol. In my experience, to access a WHOIS client you need to be on the web with a browser, but with this client all you need is to be connected to the Internet, and you will be able to access website information from the comfort of your desktop.
Because this application is about finding out as much information about a particular domain as possible, I've included another way to get information: DNS resolving. DNS resolving involves finding the IP address by converting a hostname(basically the domain name) to its IP address(es). More on this later. Let's start by explaining what a WHOIS Client is.
What is a WHOIS Client?
A WHOIS client is a program that queries a WHOIS database for information about a particular domain or person. On a technical level, WHOIS is based on a query/response communication between a client and server. WHOIS is defined in RFC 954, as stated in the introduction, but we do not have a standardized way of retrieving data from a WHOIS database. You can make the following queries with a whois client:
Search by name:
Command line: Smith Response:
Smith [looks for name or handle SMITH] !SRI-NIC [looks for handle SRI-NIC only] .Smith, John [looks for name JOHN SMITH only]
Adding "..." to the argument will match anything from that point, e.g. "ZU..." will match ZUL, ZUM, etc.
Command line: fischer Response:
Fischer, Charles (CF17) fischer@UWISC (608) 262-1204 Fischer, Herman (HF) HFischer@USC-ECLB (818) 902-5139 Fischer, Jeffery H. (JHF1) FISCHER@LL-XN (617) 863-5500 ext 4403 or 4689 Fischer, Kenneth (KF8) SAC.SIUBO@USC-ISIE (402) 294-5161 (AV) 271-5161 Fischer, Marty (MF28) MFISCHER@DCA-EMS (703) 437-2344 Fischer, Michael J. (MJF) FISCHER@YALE (203) 436-0744 Fischer, Nancy C. (NANCY) FISCHER@SRI-NIC (415) 859-2539 Fischer, Richard A. (RAF4) Fisher Richa@LLL-MFE (415) 422-5032
To single out any individual entry, repeat the command using the argument "!HANDLE" instead of "NAME", where the handle is in parentheses following the name.
To query the full details of a person: Command line: !nancy Response:
Fischer, Nancy C. (NANCY) FISCHER@SRI-NIC SRI International
Telecommunication Sciences Center
333 Ravenswood Avenue, EJ289
Menlo Park, California 94025
Phone: (415) 859-2539
MILNET TAC user
Search by mailbox:
Smith@ [looks for mailboxes with username SMITH] @Host [looks for mailboxes on HOST] Smith@Host [Looks for mailboxes with username SMITH on HOST]
Other than the above specifications, the protocol pretty much leaves it up to us to define how to query a WHOIS database, as well as what kind of information we should include in a WHOIS database.
A WHOIS database contains name server, registrar, and in some cases, full contact information about a domain name. Each registrar must maintain a WHOIS database containing all contact information for the domains they "host." A central registry WHOIS database is maintained by the InterNIC. This database contains only registrar and name server information for all .com, .net and .org domains. Again, the RFC does not specify how much information should be kept about a particular person or registrant. And as a result you get WHOIS databases with varying levels of information. We are not going to implement the database aspect of the WHOIS in this article, as it is an entire story unto itself.
Delphi-Kylix 
Building an IRC Client
