A non-UNIX socket program can use only one TCP/IP protocol stack at a time. The native TCP/IP C socket library is not POSIX compliant and it should not be used for new C socket program development. The non-C native TCP/IP socket libraries (sockets extended: call and assembler macro, REXX sockets, CICS® sockets, and IMS™ sockets) are available for development of new socket application programs. The following TCP/IP Services APIs are included in this library:

Pascal API

The Pascal IPv4 socket application programming interface enables you to develop TCP/IP applications in the Pascal language. Supported environments are normal MVS™ address spaces. The Pascal programming interface is based on Pascal procedures and functions that implement conceptually the same functions as the C socket interface. The Pascal routines, however, have different names than the C socket calls. Unlike the other APIs, the Pascal API does not interface with z/OS® UNIX System Services; it uses an internal interface to communicate with the TCP/IP protocol stack.

IMS sockets

The Information Management System (IMS) IPv4 socket interface supports development of client/server applications in which one part of the application executes on a TCP/IP-connected host and the other part executes as an IMS application program. The programming interface used by both application parts is the socket programming interface, and the communication protocols are either TCP, UDP, or RAW. For more information, see z/OS Communications Server: IP IMS Sockets Guide.

CICS sockets

The CICS socket interface enables you to write CICS applications that act as IPv4 or IPv6 clients or servers in a TCP/IP-based network. Applications can be written in C language, using the C sockets programming, or they can be written in COBOL, PL/I, or assembler, using the Extended Sockets programming interface. For more information, see z/OS Communications Server: IP CICS Sockets Guide.

z/OS CS TCP/IP C/C++ Sockets

The C/C++ Sockets interface supports IPv4 socket function calls that can be invoked from C/C++ programs.

Note: Use of the UNIX C socket library is encouraged.

Sockets Extended macro API

The Sockets Extended macro API is a generalized assembler macro-based interface to IPv4 and IPv6 socket programming. It includes extensions to the socket programming interface, such as support for asynchronous processing on most sockets function calls.

Sockets Extended Call Instruction API

The Sockets Extended Call Instruction API is a generalized call-based interface to IPv4 and IPv6 sockets programming. The functions implemented in this call interface resemble the C-sockets implementation, with some extensions similar to the sockets extended macro interface.

REXX sockets

The REXX sockets programming interface implements facilities for IPv4 and IPv6 socket communication directly from REXX programs by way of an address rxsocket function. REXX socket programs can execute in TSO, online, or batch.