SAP Web AS Communication Protocols and Interfaces SAP BASIS

Inside R/3, communication is an overall process that involves most of the components of the systems both internally and to the exterior world (external systems). Communication among systems, modules, and components is based on protocols. The Web AS basis system supports most standard and de facto standard communication and networking protocols. At the operating system level, the protocol used is TCP/IP. Communication with the database is accomplished using remote SQL calls. Between applications there are many different programming interfaces that use an underlying communication layer, such as CPIC, RFC, ALE, EDI, BAPIs, and HTTP and SOAP in SAP Web AS 6.40. The communication interfaces are deployed to integrate all layers of the client/server architecture, from database server to application server to presentation servers.

Additionally, they define the channels for the exchange of electronic information, such as the input of data from external systems and the exchange of standardized business information using ALE EDI. The communication interfaces are also deployed for sending and receiving mail from the exterior world (Internet, for example) using the standard X.400 mail protocol. At the programming level, the Web AS system uses the CPIC protocol for program-toprogram communication and also includes support for remote function calls (RFCs) Microsoft OLE interface, ActiveX, and many other standard interfaces based on objects, such as CORBA, COM/DCOM, and others. Extensive information about communication at the programming level can be found in the Web AS online documentation. SAP also provides support for connecting and exchanging data and information with traditional mainframes using SNA or other standard protocols. The system has utilities that enable communication and data exchange with special peripheral devices such as presence card readers and production plant devices.

Common Programming Interface Communications

CPIC (Common Programming Interface Communications) is the interface deployed by the ABAP language for program-to-program communication. CPIC was defined and developed by IBM as a standardized communication interface and was later modified and enhanced by the X/Open organization. The CPIC interface is useful when setting up communications and data conversion and exchange between programs. Because CPIC is based on a common interface, an additional advantage is the portability of the programs across different hardware platforms. SAP divides the possibilities and the scope of the CPIC interface into two function groups: the CPIC starter set and the advanced function calls. This division is simply meant to guide the user and not to restrict the available functions. For instance, the CPIC starter set would just be used for the basic and minimum set of functions shared by two partner programs, such as establishing the connection and exchanging data. The advance calls cover more communication functionality, such as converting data, checking the communication, and applying security functions. For more information on these CPIC function groups, refer to the SAP documentation BC SAP Communication; CPI-C Programmer's Guide. CPIC communication is always performed using the internal SAP gateway that takes care of converting the CPIC calls to external communication protocols such as TCP/IP.

Remote Function Calls

RFC (remote function calls) is a standard programming interface for making remote calls between programs located on different systems. Functions that are developed or exist in a system can be remotely called by another local program. This is particularly useful for data manipulation and processing load balancing between systems. Even when the same functions exist on both systems—called and caller—it is a way of making another system send or receive data, and the remote CPU assigns the needed resources. RFC is a higher-level logical interface than CPIC, and it makes life easier for programmers because they do not have to worry about implementing communication routines. With the RFC interface, function calls can be accomplished between two SAP systems or between SAP systems and external ones (for instance, with Microsoft Windows applications). The library functions included with RFC support the Visual Basic and C programming languages on Windows platforms. The RFC interfaces come basically with two services:

  • A calling interface for the ABAP programs. Any ABAP program can call a remote function using standard programming sentences, providing the remote system has allowed the module to be called remotely.
  • An RFC API (application program interface) for programs other than ABAP (non-SAP). SAP even provides an RFC program generator to help implement RFC partner programs in external systems. With these API calls, external programs can call ABAP function modules in SAP Web AS systems (also in R/2).

At the same time, with the RFC API, ABAP programs can use functions provided by external programs. SAP online help and the documentation print files include extensive information about remote programming with RFC and the RFC API.

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