Create Functions for ESPs

A function that implements an ESP must be written in a procedural programming language that is capable of calling a C-language function, manipulating C-language datatypes, and linking with the Open Server API. .

However, an ESP function should not call a C runtime signal routine on Windows. This can cause XP Server to fail, because Open Server does not support signal handling on Windows.

By using the Open Client API, an ESP function can send requests to SAP ASE, either to the one from which it was originally invoked or to another one.

• Files for ESP Development
  To use the Open Server libraries for development, you must first purchase an Open Server license. The header files needed for ESP development are in $SAP/$SAP_OCS/include.
• Open Server Data Structures
  Certain data structures are available for writing ESP functions.
• Open Server Return Codes
  Open Server functions return a code of type CS_RETCODE.
• Outline of a Simple ESP Function
  An ESP function should follow a certain structure with regard to its interaction with the Open Server API.
• ESP Function Example
  xp_echo.c includes an ESP that accepts a user-supplied input parameter and echoes it to the ESP client, which invokes the ESP. An example demonstrates the inclusion of the xp_message function, which sends messages and status, and the xp_echo function which processes the input parameter and performs the echoing.
• Building the DLL
  To compile a function that uses the Open Server API, you can use any compiler that can produce the required DLL on your server platform.