Programming Interfaces Guide

Overview of Sockets

Sockets have been an integral part of SunOS releases since 1981. A socket is an endpoint of communication to which a name can be bound. A socket has a type and an associated process. Sockets were designed to implement the client-server model for interprocess communication where:

Sockets make network protocols available while behaving like UNIX files. Applications create sockets as sockets are needed. Sockets work with the close(2), read(2), write(2), ioctl(2), and fcntl(2) interfaces. The operating system differentiates between the file descriptors for files and the file descriptors for sockets.

Socket Libraries

The socket interface routines are in a library that must be linked with the application. The library is contained in /usr/lib with the rest of the system service libraries. Use for dynamic linking.

Socket Types

Socket types define the communication properties that are visible to a user. The Internet family sockets provide access to the TCP/IP transport protocols. The Internet family is identified by the value AF_INET6, for sockets that can communicate over both IPv6 and IPv4. The value AF_INET is also supported for source compatibility with old applications and for “raw” access to IPv4.

The SunOS environment supports three types of sockets:

See Selecting Specific Protocols for further information.

Interface Sets

The SunOS 5.9 platform provides two sets of socket interfaces. The BSD socket interfaces are provided and, since SunOS™ version 5.7, the XNS 5 (Unix98) socket interfaces are also provided. The XNS 5 interfaces differ slightly from the BSD interfaces.

The XNS 5 socket interfaces are documented in the following man pages:

The traditional BSD Socket behavior is documented in the corresponding 3N man pages. In addition, the following new interfaces have been added to section 3N:

See the standards(5) man page for information on building applications that use the XNS 5 (Unix98) socket interface.