Certain data structures are available for writing ESP functions.
SRV_PROC – all ESP functions are coded to accept a single parameter, which is a pointer to a SRV_PROC structure. The SRV_PROC structure passes information between the function and its calling process. ESP developers cannot directly manipulate this structure.
The ESP function passes the SRV_PROC pointer to the Open Server routines that get parameter types and data and return output parameters, status codes, and result sets.
CS_SERVERMSG – Open Server uses the CS_SERVERMSG structure to send error messages to a client using the srv_sendinfo routine. See the Open Server-Library/C Reference Manual for information about CS_SERVERMSG..
CS_DATAFMT – Open Server uses the CS_DATAFMT structure to describe data values and program variables.