To build today's highly distributed, networked applications and services, you need deep mastery of sockets and other key networking APIs. One book delivers comprehensive, start-to-finish guidance for building robust, high-performance networked systems in any environment: UNIX Network Programming, Volume 1, Third Edition.

The late W. Richard Stevens was the original author of UNIX Network Programming, First and Second Editions, widely recognized as the classic texts in UNIX networking Bill Fenner is Principal Technical Staff Member at AT&T Labs in Menlo Park, CA Andrew M. Rudoff, Senior Software Engineer at Sun Microsystems

Preface Introduction This book is for people who want to write programs that communicate with each otherusing an application program interface (API) known as sockets. Some readers may bevery familiar with sockets already, as that model has become synonymous with networkprogramming. Others may need an introduction to sockets from the ground up. Thegoal of this book is to offer guidance on network programming for beginners as well asprofessionals, for those developing new network-aware applications as well as thosemaintaining existing code, and for people who simply want to understand how the networkingcomponents of their system function. All the examples in this text are actual, runnable code tested on Unix systems.However, many non-Unix systems support the sockets API and the examples arelargely operating system-independent, as are the general concepts we present. Virtuallyevery operating system (OS) provides numerous network-aware applications such asWeb browsers, email clients, and file-sharing servers. We discuss the usual partitioningof these applications into client and server and write our own small examples of thesemany times throughout the text. Presenting this material in a Unix-oriented fashion has the natural side effect of providingbackground on Unix itself, and on TCP/IP as well. Where more extensive backgroundmay be interesting, we refer the reader to other texts. Four texts are so commonlymentioned in this book that we've assigned them the following abbreviations: APUE: Advanced Programming in the UNIX Environment Stevens 1992 TCPv1: TCP/IP Illustrated, Volume 1 Stevens 1994 TCPv2: TCP/IP Illustrated, Volume 2 Wright and Stevens 1995 TCPv3: TCP/IP Illustrated, Volume 3 Stevens 1996 TCPv2 contains a high level of detail very closely related to the material in this book, asit describes and presents the actual 4.4BSD implementation of the network programmingfunctions for the sockets API (socket, bind, connect, and so on). If one understandsthe implementation of a feature, the use of that feature in an application makesmore sense. Changes from the Second Edition Sockets have been around, more or less in their current form, since the 1980s, and it is atribute to their initial design that they have continued to be the network API of choice.Therefore, it may come as a surprise to learn that quite a bit has changed since the secondedition of this book was published in 1998. The changes we've made to the text aresummarized as follows: This new edition contains updated information on IPv6, which was only in draft form at the time of publication of the second edition and has evolved somewhat. The descriptions of functions and the examples have all been updated to reflect the most recent POSIX specification (POSIX 1003.1-2001), also known as the Single Unix Specification Version 3 . The coverage of the X/Open Transport Interface (XTI) has been dropped. That API has fallen out of common use and even the most recent POSIX specification does not bother to cover it. The coverage of TCP for transactions (T/TCP) has been dropped. Three chapters have been added to describe a relatively new transport protocol, SCTP. This reliable, message-oriented protocol provides multiple streams between endpoints and transport-level support for multihoming. It was originally designed for transport of telephony signaling across the Internet, but provides some features that many applications could take advantage of. A chapter has been added on key management sockets , which may be used with Internet Protocol Security (IPsec) and other network security services. The machines used, as well as the versions of their variants of Unix, have all been updated, and the examples have