From an External Program to R/2 (SAP Library - SAP Communication: CPI-C Programming (BC-CST-GW))

From an External Program to R/2

Purpose

A non-SAP program uses an RFC or CPI-C call CMINIT/CMALLC to start an ABAP program in an R/3 System, and exchanges data with the ABAP program.

Prerequisites / Process flow

With this constellation, you must note the following guidelines:

Using the RFC interface:

The RFC interface is available for R/2 as of Release 5.0D.

A calling C program (ANSI-C) must be structured as follows:

:
#include "saprfc.h"
:
main(int argc,char **argv)
{
:
Rfc_Handle handle;
handle=RfcOpen(RFC_OPTIONS *options????)
:
}

To link the C program, use the RFC library librfc.a.

A calling Visual Basic program must be structured as follows:

:
Sub Main()
gCommand$ = Command$
:
hRfc = RfcOpenExt(gCommand$)
:
End Sub

To link the Visual Basic program, use the librfc.lib (Windows) or ntlibrfc.lib libraries.

The following DLLs are used:

librfc.dll
librfc2.dll
nidll.dll (for Windows only)

The called function must be an ABAP function module, which has the "remote" ID in the function library.

For more details on the RFC interface, refer to the documentation Remote Communications.

Using the CPI-C interface

The SAP Gateway must be in use.
The calling program (ANSI-C) must be structured as follows:

:
< poss. host type define, see Define Variables for Host Types >
:
#define SOCK 1
#include "cpic.h"
:
main(int argc,char **argv)
{
:
SAP_CMINIT(argv,<P2>,<P3>,<P4>);
:
CMINIT(..);
:
}

To link the C program, use the function library cpictlib.o.

Parameterization

Via SAP_CMINIT:

For communication with the gateway, you must use the function SAP_CMINIT to pass the following parameters to the CPI-C interface:

P2:	Gateway host
P3:	Gateway service
P4:	Protocol type/topology of the target program: C, I or E
C:	Partner is the R/2 program
I:	Partner is the R/3 program and can be reached via TCP/IP
E:	Partner is an external program and can be reached via TCP/IP

The necessary constants are defined in the C header cpic.h.

If an error occurs, SAP_CMINIT delivers a return code not equal to CM_OK.

Side Info File:

You can also maintain these parameters in the side information file. In this case, call the function SAP_CMINIT as follows:

SAP_CMINIT(argv,(PCPIC_CHAR)0,(PCPIC_CHAR)0,NO_PROTOCOL);

After calling SAP_CMINIT you can use CPI-C programming as usual.

You can also specify some parameters with SAP_CMINIT and read some from the side information file.

You must include target system and platform-dependent entries in the side information file.

For details on the configuration of the side information file, refer to the relevant topic in the following documentation:

BC SAP Communication: Configuration

If timeouts occur when establishing a connection, you can use the environment variable CPIC_TIMEOUT to extend the wait time. CPIC_TIMEOUT specifies the time in seconds, which the gateway waits for the external program logon.

The pointer passed when SAP_CMACCP is called cannot point to data in the stack.

This is because the pointer is also used in the subsequent CPI-C functions.