monovm-whois-ruby

https://github.com/monovm/whois-ruby

Look up domain registration data and check availability over RDAP and WHOIS (port 43). Prefers RDAP where a registry offers it, falls back to port 43, follows registrar referrals for thin registries, and parses records into structured objects. Availability detection is a priority-ordered rule chain that reports "unknown" instead of guessing when a server refuses to answer. No runtime dependencies.