A UNIX socket program can use up to eight TCP/IP protocol stacks at once. The stacks may be a combination of any TCP/IP protocol stack that is supported by z/OS® UNIX System Services. The following APIs are provided by the UNIX element of z/OS and are not addressed in detail in this publication:

z/OS C sockets

z/OS UNIX C sockets are used in the z/OS UNIX environment. Programmers use this API to create IPv4 and IPv6 applications that conform to the POSIX or XPG4 standard (a UNIX specification). Applications built with z/OS UNIX C sockets can be ported to and from platforms that support these standards. For more information, see z/OS XL C/C++ Runtime Library Reference.

z/OS UNIX Assembler Callable Services

z/OS UNIX Assembler Callable Services is a generalized call-based interface to z/OS UNIX IPv4 and IPv6 sockets programming. The functions implemented in this call interface resemble the z/OS UNIX C sockets implementation, with some extensions similar to the sockets extended macro interface. For more information, see z/OS UNIX System Services Programming: Assembler Callable Services Reference.