# File resolv.rb, line 570
        def initialize
          super()
          @sock = UDPSocket.new
          @sock.fcntl(Fcntl::F_SETFD, 1) if defined? Fcntl::F_SETFD
          @id = {}
          @id.default = -1
          @thread = Thread.new {
            DNSThreadGroup.add Thread.current
            loop {
              reply, from = @sock.recvfrom(UDPSize)
              msg = begin
                Message.decode(reply)
              rescue DecodeError
                STDERR.print("DNS message decoding error: #{reply.inspect}\n")
                next
              end
              if s = @senders[[[from[3],from[1]],msg.id]]
                s.recv msg
              else
                #STDERR.print("non-handled DNS message: #{msg.inspect} from #{from.inspect}\n")
              end
            }
          }
        end

# File resolv.rb, line 595
        def sender(msg, data, queue, host, port=Port)
          service = [host, port]
          id = Thread.exclusive {
            @id[service] = (@id[service] + 1) & 0xffff
          }
          request = msg.encode
          request[0,2] = [id].pack('n')
          return @senders[[service, id]] =
            Sender.new(request, data, @sock, host, port, queue)
        end