This book provides the information and tools you need to excel at these tasks.<br><br>Your job will not be easy. Networked applications are often much harder to design, implement, debug, optimize, and monitor than their stand-alone counterparts. You must learn how to resolve the inherent and accidental complexities [Bro87] associated with developing and configuring networked applications. Inherent complexities arise from key domain challenges that complicate networked application development, including<br><br>Selecting suitable communication mechanisms and designing protocols to use them effectively<br><br>Designing network services that utilize the available computing resources efficiently and reduce future maintenance costs<br><br>Using concurrency effectively to achieve predictable, reliable, high performance in your system<br><br>Arranging and configuring services to maximize system availability and flexibility.<br><br>Dealing with inherent complexity requires experience and a thorough understanding of the domain itself. There are many design tradeoffs related to these inherent complexity issues that we will investigate in Chapters 1 and 5.<br><br>Accidental complexities arise from limitations with tools and techniques used to develop networked application software, including<br><br>The lack of type-safe, portable, and extensible native OS APIs<br><br>The widespread use of algorithmic decomposition, which makes it unnecessarily hard to maintain and extend networked applications<br><br>The continual rediscovery and reinvention of core networked application concepts and capabilities, which keeps software life-cycle costs unnecessarily high<br><br>
Microsoft Windows作业系统提供了许多工具让服务器端之主从式应用程序部份的实作变得更容易。如您所知，一个服务器即是一个履行服务器端义务的Windows应用程序。事实上，Microsoft BackOffice Logo程序即要求服务器应用程序应被实作成如同服务（services）一般的程序。 <br>服务是含有附加基础，允许它根据作业系统而受到特别处理的一般Windows应用程序，例如，远端管理的能力，允许管理者从一个远端的机器来启动或停止应用程序的执行。您将免费取得将您的服务器应用程序转成一个服务程序的方式以及其他相关的特性。本章将会解释服务的内容、如何设计一个服务应用程序与作业系统为服务提供了什么附加的工具等。<br><br>
UNIX Systems Programming: Communication, Concurrency and Threads is the second edition of Practical UNIX Programming: A Guide to Communication, Concurrency and Multithreading, which was published by Prentice Hall in 1995. We changed the title to better convey what the book is about. Several things have changed, besides the title, since the last edition.<br><br>The Internet has become a dominant aspect of computing and of society. Our private information is online; our software is under constant attack. Never has it been so important to write correct code. In the new edition of the book, we tried to produce code that correctly handles errors and special situations. We realized that saying handle all errors but giving code examples with the error handling omitted was not effective. Unfortunately, error handling makes code more complex. We have worked hard to make the code clear.<br><br>Another important development since the last edition is the adoption of a Single UNIX Specification, which we refer to as POSIX in the book. We no longer have to decide which vendor's version of a library function to use—there is an official version. We have done our best to comply with the standard.<br><br>The exercises and projects make this book unique. In fact, the book began as a project workbook developed as part of a National Science Foundation Grant. It became clear to us, after preliminary development, that the material needed to do the projects was scattered in many places—often found in reference books that provide many details but little conceptual overview. The book has since evolved into a self-contained reference that relies on the latest UNIX standards.<br><br>
This book is for people who want to write programs that communicate with each other using an application program interface (API) known as sockets. Some readers may be very familiar with sockets already, as that model has become synonymous with network programming. Others may need an introduction to sockets from the ground up. The goal of this book is to offer guidance on network programming for beginners as well as professionals, for those developing new network-aware applications as well as those maintaining existing code, and for people who simply want to understand how the networking components of their system function.<br><br>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 are largely operating system-independent, as are the general concepts we present. Virtually every operating system (OS) provides numerous network-aware applications such as Web browsers, email clients, and file-sharing servers. We discuss the usual partitioning of these applications into client and server and write our own small examples of these many times throughout the text.<br><br>Presenting this material in a Unix-oriented fashion has the natural side effect of providing background on Unix itself, and on TCP/IP as well. Where more extensive background may be interesting, we refer the reader to other texts. Four texts are so commonly mentioned in this book that we've assigned them the following abbreviations: <br><br>APUE: Advanced Programming in the UNIX Environment [Stevens 1992]<br><br>TCPv1: TCP/IP Illustrated, Volume 1 [Stevens 1994]<br><br>TCPv2: TCP/IP Illustrated, Volume 2 [Wright and Stevens 1995]<br><br>TCPv3: TCP/IP Illustrated, Volume 3 [Stevens 1996]<br><br>
Today, there are three primary sets of multithreading (MT) libraries: the<br>“standards-based” libraries (all of the UNIX® implementations and VMS, which<br>are moving to POSIX), the OS/2® library, and the Win32 library. (The NT and<br>OS/2 libraries are fairly similar, which should not be too surprising. NT did start<br>life as OS/2, version 2, after all.) Although the APIs1 and implementations differ<br>significantly, the fundamental concepts are the same. The ideas in this book are<br>valid for all three; the details of the APIs differ.<br>All the specific discussion in this book focuses on the POSIX multithreading<br>model, with comparisons to OS/2 and Win32 throughout.<br>A frank note about our motivation is in order here. We have slaved away for<br>countless hours on this book because we’re propeller-heads who honestly believe<br>that this technology is a superb thing and that the widespread use of it will make<br>the world a better place for hackers like ourselves.<br>Your motivations for writing MT programs? You can write your programs better<br>and more easily, they’ll run faster, and you’ll get them to market more quickly,<br>they’ll have fewer bugs, you’ll have happier programmers, customers, and higher<br>sales. The only losers in this game are the competitors, who will lag behind you<br>in application speed and quality.<br>MT is here today. It will soon be ubiquitous. As a professional programmer, you<br>have an obligation to understand this technology. It may or may not be<br>appropriate for your current project, but you must be able to make that<br>conclusion yourself. This book will give you what you need to make that<br>decision.<br>Welcome to the world of the future!
