Simple DNS server in ruby. Tested and it works!

dnsserv.rb

#!/usr/bin/env ruby

require 'rubygems'
require 'rubydns'

$R = Resolv::DNS.new
Name = Resolv::DNS::Name
IN = Resolv::DNS::Resource::IN
Hosts = "/etc/dnsserv/hosts"

RubyDNS::run_server(:listen => [[:udp, "0.0.0.0", 5300]]) do
  # For this exact address record, return an IP address
  match(/.*/) do |transaction|
    line = `grep "#{transaction.name}" #{Hosts}`.split("\n").first
    transaction.passthrough!($R) if $?.exitstatus != 0
    ip = line.split("\t").first
    transaction.respond!(ip)
  end

  # Default DNS handler
  otherwise do |transaction|
    transaction.passthrough!($R)
  end
end

hosts

10.0.0.80 dev.test.org
8.8.8.8 dns.gg.com