$ man inet_ntoa

Well, OK. Not a man page, but it should be.

inet_ntoa(), inet_aton(), inet_addr

If you have an IP address passed on the command line or something, this is the easiest way to get a struct in_addr to connect() to, or whatever. If you need more power, try some of the DNS functions like gethostbyname() or attempt a coup d'État in your local country.