fetch_resource

# File lib/resolv.rb, line 515
    def fetch_resource(name, typeclass)
      lazy_initialize
      requester = make_udp_requester
      senders = {}
      begin
        @config.resolv(name) {|candidate, tout, nameserver, port|
          msg = Message.new
          msg.rd = 1
          msg.add_question(candidate, typeclass)
          unless sender = senders[[candidate, nameserver, port]]
            sender = requester.sender(msg, candidate, nameserver, port)
            next if !sender
            senders[[candidate, nameserver, port]] = sender
          end
          reply, reply_name = requester.request(sender, tout)
          case reply.rcode
          when RCode::NoError
            if reply.tc == 1 and not Requester::TCP === requester
              requester.close
              # Retry via TCP:
              requester = make_tcp_requester(nameserver, port)
              senders = {}
              # This will use TCP for all remaining candidates (assuming the
              # current candidate does not already respond successfully via
              # TCP).  This makes sense because we already know the full
              # response will not fit in an untruncated UDP packet.
              redo
            else
              yield(reply, reply_name)
            end
            return
          when RCode::NXDomain
            raise Config::NXDomain.new(reply_name.to_s)
          else
            raise Config::OtherResolvError.new(reply_name.to_s)
          end
        }
      ensure
        requester.close
      end
    end