Whois is a very simple text-based protocol. It has traditionally been used to retrieve information about domain names and related resources, but a Whois server can also be implemented to provide other information.
To use the Whois protocol, the client connects to port 43/tcp on the server and sends a request, which is terminated by ␍␊. As the protocol is so straightforward, the value added by dedicated Whois clients and by web-based lookup services is often minor. As long as your firewall allows outbound traffic on port 43/tcp and you know the host name of the Whois server, you should be able to do nicely with a telnet client (most popular operating systems include one).
What you need
- The host name of the Whois server (for use in the telnet command)
- A string of text for which to request information
What to do
The initial telnet: > symbolises your shell prompt.
As you can see, all you needed to do after connecting to the server was type the search string and press ⏎. The server then returned the information it had, and terminated the connection.