The EDCXSRVN routine is used by the stub routines that are linked
with user application routines to send a message to an active server
in a user-server application. EDCXSRVN has the following parameters:
- The address of the handle returned by EDCXSRVI.
- The function code for the function to be performed. The value
-1 is used to indicate that the server should terminate. This value
should not be used for any other purpose.
- Other parameters, which are passed to the server code.
Upon return, R15 will contain the return code supplied by the server
(as the parameter to EDCXSACC) for this service.