Communications Server offers mainframe network security and enables SNA and TCP/IP applications running on z/OS® to communicate with partner applications and users on the same or different systems. It enables users to enter the shell environment by using rlogin or telnet from a workstation in the TCP/IP network.

User-written socket applications can use TCP/IP services as a communication vehicle. Both client and server socket applications can use the socket interface to communicate over the Internet (AF_INET and AF_INET6) and between other socket applications by using local sockets (AF_UNIX). An assembler interface is also provided for those applications that do not use the C/C++ runtime library.

For information about multiple transport providers, see Setting up for sockets.