Introduction to Networking

The purpose of this book is to show you how to make network-aware applications that
run on the Microsoft Windows and Windows NT operating systems using the Windows
Sockets (WinSock) Application Programming Interface (API). To that end, several
practical examples are examined that utilize the basic functionality of WinSock.
Network operating systems, such as Windows for Workgroups and Windows NT,
provide basic file and printer sharing services. This most basic level of functionality is
provided “out of the box.” Network-aware applications are programs that use the capabilities
of a collection of connected computers. Network-aware programs range from
custom applications that transfer data among computers on a network to mainstream
applications that enable electronic mail and remote database access. The WinSock API
is a library of functions that a programmer can use to build these network-aware
applications. WinSock has its roots in Berkeley sockets as introduced in the Berkeley
Software Distribution of UNIX. WinSock uses the TCP/IP (Transmission Control Protocol/
Internet Protocol) suite, which provides the formal rules of behavior that govern
network communications between all computers running this particular computer networking
protocol.
Before I begin the examination of network programming, look at the basics of computer
networking in general. A network can be loosely defined as a collection of two or
more computers that have some sort of communication path between them. A network
can be loosely classified as either a local area network (LAN) or wide-area network
(WAN). The use of the terms LAN and WAN is somewhat misleading because which
term you use is relative to the particular network installation you’re describing. Generally
speaking, a LAN covers a much more geographically restricted area than does a WAN.
Whereas a LAN may connect computers within an office building, a WAN may connect
computers spread across the country. With the advances in networking hardware
and software, many widely dispersed LANs can now be connected to form a much larger
homogeneous WAN. Devices known as bridges and routers allow for this connection of
disparate LANs. Computer networks aren’t new, but they weren’t accepted in the personal
computer realm until perhaps the late 1980s, when computer firms began offering
cost-effective and reliable networking for the desktop PC. At that time, the primary
goal of the PC network was to provide a central repository for files and to allow printers
to be shared among many users. It hasn’t been until relatively recently that businesses
have realized the true potential of a PC network.

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