let rec accept_connection sock =
  let socket_thread = Lwt_unix.accept sock  in
  Lwt.bind socket_thread
           ( fun (fd, caller) ->
               ignore(Lwt_io.printf "accepted\n%!");
                readall fd >>= fun a -> Lwt_io.printf "readall result\n %s\n%!" a >>= fun () -> Lwt_unix.close fd
               accept_connection sock;
           );;