Difficulties understanding aceserver access control

[Jean Thierry-Mieg]

you are right
the documentation is inconsistent with the behaviour

but not quite
the idea is that at least the administrator must have write privildge
so the write_dir must exist

what happen is that the server simply crashes
you must provide a dir where the server itself can write and nobody can
read

that is a dir which belongs to the admin user who runs the server
and which is 700 rwx------