How to implement your own WHOIS server?

Question

How would you get the WHOIS information to provide in the first place?

Note that I'm not actually intending to do this; I'm just interested in how it would work!

Answer 1

Simply implement the whois protocol https://www.rfc-editor.org/rfc/rfc3912

You get a query, you look it up in your database and you send your answer. That's it. Have a look at the example:

   open TCP   ---- (SYN) ------------------------------>
              <---- (SYN+ACK) -------------------------
   send query ---- "Smith<CR><LF>" -------------------->
   get answer <---- "Info about Smith<CR><LF>" ---------
              <---- "More info about Smith<CR><LF>" ----
   close      <---- (FIN) ------------------------------
              ----- (FIN) ----------------------------->

How to build your own database, it depends on what information you want to provide.