gistfile1.rb

#!/usr/bin/env ruby

require 'socket'
require 'thread'

def foo
  queue = Queue.new
  semaphore = Mutex.new
  threads = 16
  (1000).times {|i| queue << i } # obviously this isn't going to work :(
  threads.times.map {
    until queue.empty?
      Thread.new do
        begin
          addr = [queue.pop].pack('V').unpack('C4')
          name = Socket.gethostbyaddr(addr.pack('C4')).first
          semaphore.synchronize {
            yield addr.join('.'), name if block_given?
          }
        rescue SocketError => serr
          semaphore.synchronize {
            yield addr.join('.'), serr.message if block_given?
          }
        end
      end
    end
  }.each(&:join)
end


foo { |addr, name| puts "#{addr}  --->  #{name}" }