Different WHOIS Protocols

Comparison of the description of the WHOIS protocol (getting domain name or IP information) between RFC 812, RFC 954, and RFC 3912. RFC 3912 is the latest version replacing RFC 954 which in turn replacing RFC 812. I prefer the writing style of RFC 954, simple and direct.

a) RFC 812

Connect to the service host (SRI-NIC)
      TCP: service port 43 decimal
      NCP: ICP to socket 43 decimal, establishing two 8-bit connections

Send a single "command line", ending with .

Receive information in response to the command line.  The server closes its connections as soon as the output is finished.

b) RFC 954.

Connect to the SRI-NIC service host at TCP service port 43 (decimal).

Send a single "command line", ending with (ASCII CR and LF).

Receive information in response to the command line.  The server closes its connection as soon as the output is finished.

c) RFC 3912
"A WHOIS server listens on TCP port 43 for requests from WHOIS clients.  The WHOIS client makes a text request to the WHOIS server, then the WHOIS server replies with text content.  All requests are terminated with ASCII CR and then ASCII LF.  The response might contain more than one line of text, so the presence of ASCII CR or ASCII LF characters does not indicate the end of the response.  The WHOIS server closes its connection as soon as the output is finished. The closed TCP connection is the indication to the client that the response has been received."
Some hands-on exercises using whois and telnet program. We're connection to whois.iana.org because we want to find the root domain name server against the Root Zone Database.

a) whois command
$ whois -h whois.iana.org com | less

b) telnet command. Press enter after you've type the domain extension. You can type any domain name as well.
$ telnet whois.iana.org 43
Trying 192.0.32.59...
Connected to ianawhois.vip.icann.org.
Escape character is '^]'.
com

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