server-can-exit-p returns true if the server can exit, which means that the server is not in use (that is,
(not (server-in-use-p)) returns
t, and also that there are no other "working processes", which means that all other processes except the one that calls
server-can-exit-p are "Internal servers" (see
The main purpose of
server-can-exit-p is to be the exit-function for automation-server-top-loop, either as the default or called from a supplied exit-function.
LispWorks COM/Automation User Guide and Reference Manual - 23 Mar 2017