This book describes the Windows Sockets application programming interface (API), commonly known as "WinSock." This is intended to be a companion to the v1.1 Windows Sockets specification, not a replacement for it. The contents provide a roadmap for the specification, an orientation resource. The book describes and illustrates every aspect of the Windows Sockets specification, from top to bottom. It deals with optional features as well as many features in version 2.0 of the Windows Sockets specification.The key focus of the text is to provide a "how to" guide for writing supportable and extensible network applications that will run efficiently over all Windows Sockets implementations. One of the most frustrating things to hear is, "It's impossible to write anything more than a basic 'hello world' that will execute over all Winsock implementations." This simply is not true. More often than not, when an application runs on one WinSock and fails on another, it is because the application developers made some incorrect assumptions. They assumed that WinSock could do something that the specification did not explicitly warrant. In other words, it may not have been the fault of the WinSock implementor, nor of the WinSock specification. You can avoid this type of application failure, and we show you how.
This book is for anyone who wants to know how to write a successful WinSock application. If you are writing a program from scratch, porting an existing one from Berkeley sockets (or any other network API), writing a network DLL, or just updating an application that someone else wrote, then this book is for you. We deal with both 16-bit Windows platforms (Microsoft Windows 3.1 and Windows for Workgroups) and 32-bit platforms (Windows NT 3.1 and 3.5, and Windows 95). We also describe the other platforms that support the WinSock API: Platforms with Windows are adding Sockets.
Organization
The first half of the book contains a tutorial for network programming. We do not make any assumptions about what you already know. The second half is intended to be an in-depth reference, with detailed explanations and code examples. The appendices provide a quick reference.After we describe Windows Sockets in general terms in Chapter 1, we provide an overview of network software architectures in Chapter 2. In Chapter 3 we describe the protocols in the TCP/IP suite, with a focus on the services available to your network applications, and some of their pros and cons. We begin to provide some details about the WinSock programming interface in Chapter 4, as we describe the framework for all network applications in terms of the fundamental network function calls. Chapter 5 covers the different operation modes available, and Chapter 6 discusses the state machine implicit in every network application. That essentially ends the tutorial.
In Chapter 7 we present the source code for our largest application, an FTP client. Chapters 8, 9, and 10 are a catalog of detailed descriptions of all the WinSock function calls we have not discussed up to this point. Chapter 11 deals with the specifics of creating a dynamic link library to run over a WinSock DLL. Chapter 12 describes the issues and strategies involved with porting existing BSD Sockets source code to 16-bit and/or 32-bit Windows.
We start to wrap things up and tie up loose ends in Chapter 13, which details WinSock application debugging techniques and tools. Chapter 14 provides general advice and many specifics about traps and pitfalls to avoid in your WinSock applications. Chapter 15 describes the many different operating-system platforms that currently provide the WinSock API. Chapter 16 covers the optional features - some intentional, and some not - in the WinSock specification and tells you when and how to use them. Finally, Chapter 17 provides a detailed tour of all the new features in version 2.0 of the WinSock specification.
In Appendix A, we have illustrations and short descriptions of the headers for protocols in the Internet suite (TCP/IP). Appendix B contains a quick reference for the entire WinSock API, including its functions, structures, and macros (including some that were forgotten). Appendix C provides a detailed WinSock error reference. Appendix D contains some mechanical details for compiling and linking applications, and Appendix E has network and bibliographical information sources.
Audience
Although we do not assume any prior knowledge of networks, protocols, or network programming with sockets or any other network API, it does not hurt to have some. This book is for novice and experienced network application developers alike. This text also includes extensive background and illustrative information not found in the v1.1 Windows Sockets specification, so even the most advanced WinSock application developer can benefit from reading it.We do assume a knowledge of the C programming language and Microsoft Windows APIs (WinAPI or Win32).
Sample Applications
The sample applications in this book were created with Microsoft C version 1.51 (16-bit) and Microsoft C version 2.0 (32-bit). They are also compatible with Borland C version 4.0. Makefiles that support these platforms accompany the source code. The applications have been tested on almost all of the commercial and shareware versions of WinSock available, over Ethernet and PPP (point-to-point protocol), using both local and distant connections. If you find any problems with these applications, we'd like to hear about them. Please e-mail problem reports to bugs@sockets.com.You can retrieve updates to these sample applications via the Internet: http://www.sockets.com.
Acknowledgments
Many thanks to people for their help and participation in making this book possible. Thanks especially to the reader, who is the very reason for this book. May your Windows Sockets applications be great ones.Thanks most of all to Bob Quinn. He wanted to give birth to this book; I only provided the hot water, towels, antiseptic, blankets, silver nitrate, topical anesthesia, and appropriate words.
Dave Shute
dks@world.std.com
Reading, MA
May 1995
There are far too many people that have helped in this endeavor for any acknowledgment list to do justice. Nonetheless, I want to mention a few people in particular. First and foremost, for their implicit contribution, is my family. It will be nice to spend time with them again. Second is my cowriter and friend, Dave Shute, whose red pencil is as pricelessly sharp as his wit.
I'm indebted to Larry Backman, Mike Khalandovsky, and John Keller at FTP Software, Inc., for their support and encouragement. Dave Barnard, Kerry Hannigan, and Helen Sylvester - FTP Software's crack SDK support staff - deserve a special note for their constant stream of challenges that did more to teach me about how to program - and how not to program - WinSock apps than anything else did.
My coadministrators in the WinSock 2.0 specification clarification functionality group, Paul Brooks and Vikas Garg, deserve a lot of credit for their untiring efforts to shed light into the dark corners of WinSock. In addition to clarifying many things in the spec, they also clarified some things in this book.
Other reviewers of note: Jim DeMarco, Fred Whiteside, Dave Andersen, Charlie Tai, Alun Jones, Eli Patashnik, and our consulting editor, Alan Feuer.
Thanks to the kind folks at Addison-Wesley: John Wait, Mike Hendrickson, Kim Dawley, Marty Rabinowitz, Simone Payment, and Katie Duffy.
Lastly, I want to thank Martin Hall for having initiated the Windows Sockets effort and his coauthors and contributors for helping him carry it through. The sure sign of a good idea is one that makes you think, "Why didn't I think of that!?" That's WinSock. It was a great idea, and its immediate success has confirmed this obvious fact.
Bob Quinn
rcq@ftp.com.
Weston, Massachusetts
May 1995
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