An external program shall call a function module via the RFC interface using the RFC library, and then display R/3 data locally on the frontend.

Create a complete RFC client program, starting from function module RFC_CUSTOMER_GET, whose interface is completely known and has been tested with current values of the transfer parameters. To do this, first generate a example program and then develop an executable application within a C development environment.

In this unit you will learn how to

• use the ABAP Workbench to generate an ANSI C client program and to transfer the program to the local frontend.
• create a project within a C development environment and to derive an executable program from it.
• use the RFC library and the most important Include files and C functions.
• assign the important program steps to the components of the R/3 architechture.

Technical prerequisites:

• The external system supports TCP/IP.
• The RFC SDK (Software Development Kit) is installed on the local system.

The following general prerequisites for remote communication must be met:

• The function to be called must be installed in the target system and flagged as "remote".
• To the target system, a Logical Destination is assigned.

External programs can use different RFC interfaces to the R/3 system either as RFC client or as RFC server. RFC is an SAP interface protocoll based on CPI-C. However, compared to the CPI-C protocoll, programming communication procedures with RFC is much easier. One of the cross-platform interfaces is the RFC library, ofter referred to as RFC API.

In contrast to a local function call, a C program as RFC client (or RFC server) needs additional administration functions to

• establish or terminate an RFC connection,
• handle functions, parameters, or tables,
• handle exceptions,
• convert RFC data types,
• control the communcation flow.

For each R/3 system, SAP delivers an RFC SDK. The RFC SDK for the respective platform contains the RFC library, several executable example applications, and several include files. The most important include files are:

• saprfc.h
  This include file contains all data types, structures, and prototypes of RFC call routines.
• saitab.h
  This include file contains prototypes of functions for handling internal tables from ABAP.

To directly access remote function modules of the R/3 system via a desktop application, you can use either a C program or a Visual Basic program that calls this function. There are two ways:

• The external program directly uses function modules of the RFC API.
• The external program uses a generated Example program, which is created as compilable source file using the RFC interface generator.

or