API support

This topic describes API support and contains the following subtopics:

z/OS provides a versatile and diverse set of socket API libraries to support the various z/OS application environments. Figure 1 illustrates the relationship of the various z/OS socket APIs and the level of IPv6 present for each API.

Figure 1. z/OS socket APIs

Shows the relationship of the various z/OS socket APIs and the level of IPv6 present for each API in a layer hierarchy.

The following environments are the two main socket API execution environments in z/OS:

UNIX [implemented by UNIX System Services (Language Environment®)]
Native TCP/IP (implemented by TCP/IP in z/OS Communications Server)

There are several higher level C/C++ APIs that rely on the TCP/IP sockets for communications over an IP network, including the following APIs:

Resource Reservation Setup Protocol API (RAPI)
Sun and NCS Remote Procedure Call (RPC)
X Window System and Motif
X/Open Transport Interface (XTI)

These APIs do not support IPv6 communications.

Guideline: CICS® programs written to use the IP CICS C Sockets API must use the TCP/IP C headers. Include the following definition to expose the required IPv6 structures, macros, and definitions in the header files:

#define __CICS_IPV6

See z/OS Communications Server: IP CICS Sockets Guide for information about using the IP CICS C Sockets API.