Programming instructions

The Internet and related technologies 5
Intranet applications
An intranet is a private LAN (Local Area Network) or WAN (Wide Area Network) that
lets you use and interact with your Internet-based applications in a secure environment.
These private networks exist in large corporations, small companies, and even home
offices. Private networks let companies and organizations determine who can share their
information and who can access it.
An intranet application is an application that works on a private intranet (network). It
differs from an Internet application only in who can access it and the location of the
client computer accessing it. An intranet application can also operate over a public
Internet. When an intranet application runs on the Internet, the application is called an
Internet application. These terms, Internet applications and intranet applications, are used
interchangeably throughout this book.
Web servers
A web server is a software program that serves web pages to requesting clients. The web
server software runs on any computer. Often people refer to the host running the
web-server software as the web server, and think of it as the hardware. However,
technically, the web server is just the software program and not the hardware.
How a web server and connecting hosts communicate
When a user at a specific IP address requests a file, the web server retrieves that file and
returns it to the requesting IP address. The contents of a file are not important to the web
server. It is the web browser that makes the request and interprets and displays the data in
the file that was returned from the web server.
When you make a request from a web server, an IP connection is made across the
Internet between the client making the request and the host running the web-server
software. As soon as a request is satisfied by the web server, the Internet connection
between the client and the host breaks. A page containing images or links to other pages
all require separate connections. Often, it takes many requests to retrieve all the
information on one web page.
Web pages
The information on the World Wide Web is presented in web pages. You can create web
pages using a series of client-side technologies. A web page can include a variety of
information: text, lists, forms for capturing data, tables for presenting data, scripts that
perform a function, multimedia content that animate pages, and so on.
No matter the content of the web page, the web browser must process and display the
page.