Chapter 8 -- Winsock IO Methods

Chapter 8

This chapter focuses on managing I/O in a Windows sockets application. Winsock features socket modes and socket I/O models to control how I/O is processed on a socket. A socket mode simply determines how Winsock functions behave when called with a socket. A socket model, on the other hand, describes how an application manages and processes I/O on a socket. Socket I/O models are independent of socket modes. You will find that socket models are available to overcome the limitations of socket modes.

Winsock features two socket modes: blocking and nonblocking. The first part of this chapter describes these modes in detail and demonstrates how an application can use them to manage I/O. As you'll see later in the chapter, Winsock offers some interesting I/O models that help applications manage communication on one or more sockets at a time in an asynchronous fashion: select, WSAAsyncSelect, WSAEventSelect, overlapped I/O, and completion port. By the chapter's end, we'll review the pros and cons of the various socket modes and I/O models and help you decide which one best meets your application's needs.

All Windows platforms offer blocking and nonblocking socket operating modes. However, not every I/O model is available for every platform. As you can see in Table 8-1, only one of the I/O models is available under current versions of Windows CE. Windows 98 and Windows 95 (depending on whether you have Winsock version 1 or 2) support most of the I/O models with the exception of I/O completion ports. Every I/O model is available on Windows NT and Windows 2000.

Table 8-1. Available socket I/O models

Platform	select	WSAAsync Select	WSAEvent Select	Overlapped	Completion Port
Windows CE	Yes	No	No	No	No
Windows 95 (Winsock 1)	Yes	Yes	No	No	No
Windows 95 (Winsock 2)	Yes	Yes	Yes	Yes	No
Windows 98	Yes	Yes	Yes	Yes	No
Windows NT	Yes	Yes	Yes	Yes	Yes
Windows 2000	Yes	Yes	Yes	Yes	Yes