If you have existing C or C++ language applications that perform the processes required by a custom server, you can use these as your user functions instead of writing new ones. If you need to create new user functions to satisfy your custom server requirements, code them as you would any C or C++ language program.
Whether you use existing user functions or write new ones, they are linked with the custom server main() function during the build process.
See Importing files into the custom server directory for information about transferring your C or C++ language user functions from the AIX file system on the pSeries computer to Blueworx Voice Response.