The Internet and the World Wide Web

Internet Programming Using VBScript and JavaScript

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Objectives

In this chapter you will:

Learn how the Internet evolved from ARPANET

Identify the protocols used to transmit data across the Internet

Identify the TCP/IP utilities that can be used to locate information about a Web site

Use HTML tags to create a Web page

Create a Web page using a text editor

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The History of the Internet

Today, most people access the Internet using an application called a Web browser

The most common Web browsers are Internet Explorer and Netscape Navigator

The browser is an example of a client application that allows your computer to communicate with other computers on the Internet

Many computers on the Internet are servers, which provide programs to clients

Examples of server-based programs include e-mail and Web page publishing

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The History of the Internet

Programming that makes it possible for client applications to communicate with server applications in a network is referred to as client-server programming

The original Internet (then called ARPANET) consisted of a relatively small number of computers that connected government agencies and a handful of participating universities

In September 1969, ARPANET consisted of a single network between UCLA, UCSB, Utah, and the Stanford Research Institute

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The History of the Internet

Each computer was called a host

By 1971 ARPANET stretched across the United States through fewer than two dozen universities

In 1976 the Internet was opened to commercial traffic

E-mail programs allow you to send electronic messages to other individuals via the Internet

Telnet programs allow you to remotely access a computer via the Internet, using the Telnet protocol

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The History of the Internet

An FTP server allows FTP clients to transfer files to and from the server

FTP is part of a suite of protocols known as TCP/IP (Transmission Control Protocol/Internet Protocol)

By the late 1980’s the number of host computers on the Internet had grown to 100,000

TCP/IP consists of a suite of protocols that allowed other programs, such as e-mail, Telnet, and FTP, to provide communication between computers via the Internet

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The History of the Internet

The Internet grew as more Internet service providers (ISPs), such as CompuServe, provided access to the Internet to greater numbers of people

On June 12, 1991, a new technology provided a means to easily locate and access cross-platform documents over the Internet

These cross-platform documents, called hypertext documents, were viewable no matter which computer platform you were using

This technology involved a new language standard, called Hypertext Markup Language (HTML), and a new protocol, called Hypertext Transfer Protocol (HTTP)

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The History of the Internet

HTML instructions, called tags, instructed a Web browser how to format and process a hypertext document

In 1993, the University of Illinois National Center for Supercomputing Applications (NCSA) released NCSA Mosaic, the first commercial Web browser

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The History of the Internet

Hypertext documents that are shared on the Internet are called Web pages, and the location address of these documents is known as a Uniform Resource Locator (URL)

Today the Internet is described as a global information system that uses TCP/IP to provide communications services

Many companies are currently developing Internet-based applications to facilitate e-commerce transactions

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How the Internet Works

Computers use a suite of protocols known as TCP/IP

TCP/IP includes a variety of other protocols: TCP, IP, Telnet, FTP, HTTP, Simple Mail Transfer Protocol (SMTP), and Network News Transfer Protocol (NNTP)

While TCP/IP establishes the basic rules for communication over the Internet, other network protocols, such as NetBEUI and IPX/SPX, establish the rules for communication between computers within private networks, called Intranets

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How the Internet Works

All computers that connect to the Internet, both clients and servers, must use the TCP/IP protocol

Because TCP/IP is a scaleable network protocol that can be used for local area networks (LANs) and wide area networks (WANs), most operating systems come with the TCP/IP software built in

If you have direct access to the Internet, then your computer has a copy of the TCP/IP software

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Transmission Control Protocol (TCP)

TCP splits the transmission into small packets, which are sent over the Internet to a destination computer

The TCP software on the destination computer reassembles the packets into the original transmission

En route to the destination computer, each data packet makes several stops, called hops, at one or more computers along the way

The computer at each stop is sometimes referred to as the gateway computer, because it plots the next leg of the journey and sends the packet on its way

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Internet Protocol (IP)

The Internet Protocol uses an addressing scheme to manage the addressing of each individual packet, to ensure that all packets make it to their final destinations

Gateway computers use the IP address to determine how to plot where the packet should go next

Virtually all Internet traffic travels via this IP routing model

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IP Address

Every computer connected to the Internet has an IP address associated with it

Each Web server has a unique computer number, such as 207.252.246.222, which is its IP address

Internet service providers (ISPs) assign a static or dynamic IP address each time a client computer connects to the Internet

A dynamic IP address will change each time the computer connects to the Internet

A static IP address is assigned to a specific computer and does not change

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IP Address

A Web server must have a static address so that the routing servers on the Internet will always know the IP address for the Web site

The IP protocol defines an IP address as a 32-bit number that consists of four sets of numbers separated by periods

These four numbers range from 0 to 255

A few IP addresses are reserved for special purposes

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IP Address

For example, the IP address 127.0.0.1 is not assigned to any computer on the Internet; it is known as the localhost, and is used to route packets to the local computer

A static IP address is purchased or leased from a large ISP

Because a finite number of IP addresses are available, the IP protocol is being upgraded to a newer version (version 6.0) that can support many more IP addresses

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HTTP Protocol

The HTTP protocol is used to send HTML documents through the Internet

With each packet, the HTTP protocol attaches a header, which contains information such as the name and location of the page being requested, the name and IP address of the remote server that contains the Web page, the IP address of the local client, the HTTP version number, and the URL of the referring page

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HTTP Protocol

It is important to know that HTTP version 1.0 is a stateless protocol

This means that when a client requests a document from the Web server, the server will return the Web page to the client and end all communications with the client

In version HTTP 1.1, the Web server and the client can maintain their connection across Web pages

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TCP/IP Utilities

There are many TCP/IP utility programs that are used to monitor the network

You can use these utilities to perform some basic diagnostic testing on your Web site

If a customer cannot view your Web site, you can use the ping utility to determine whether the Web server is connected to the Internet

Two of the more important TCP/IP utilities include ping and tracert

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Ping

The IP address of the Web site can be found using a TCP/IP utility called ping

Ping is a utility that is used to test network connectivity

When you ping a site, four packets are sent to the IP address

If the Web site is not connected, then a Request Timed Out message appears

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The Ping Utility 1

Tracert

Another TCP/IP utility used to locate the Web server is a packet-tracing utility known as tracert

Tracert provides the path that an Internet packet travels to get from the client to a server

When the packet stops at a gateway server, the server determines which path the packet should take next

Tracert lists each stop, or hop, that indicates that the packet has been routed to another server (or router)

The tracert utility can help you detect latencies, or delays, in routing packets to your Web site

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The Tracert Utility 1

TCP/IP Client Networking Software

Client for Microsoft Networks is the networking client software used by Windows-based computers

This software may already be installed on your computer

To verify that Client for Microsoft Networks is installed on your Windows 98 or Windows NT computer refer to the procedures outlined on pages 8 and 9 of the textbook

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TCP/IP Client Networking Software

To install Client for Microsoft Networks on your Windows 98 or Windows NT computer continue from previous step as listed on page 9 and 10

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TCP/IP Client Networking Software

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IP Configuration Utilities

The TCP/IP settings, such as the IP address of the client, are assigned using the Network program located in the Control Panel

The Windows operating system provides utilities to detect these TCP/IP settings

Winipcfg is the utility used for Windows 95/98 computers

Ipconfig is the utility used for Windows NT computers

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The Network Dialog Box Identification Tab

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Domain Names

A group of related Web pages, files, and directories—called a Web site—is stored on the Internet on a Web server

A domain name uniquely identifies a single Web site on the Internet (www.visualinterdev.org)

All domain names are registered in a global database known as the registry

In the early 1990’s, Web site sponsors were required to register domain names with InterNIC

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Domain Names

In 1992, InterNIC transferred the domain registration and registry maintenance responsibility to a company called Network Solutions

Network Solutions currently maintains the registry, there are many companies, called registrars, which can register the Web site domain name in the registry database

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Signing Up for a Domain Name

The registrar will have a form to query the database to determine whether your domain name is available

After finding an available domain name, you will need to fill out a request form to register the domain

An administrative, technical, or billing contact who has been previously entered into the database will have an InterNIC handle

The first time you register a domain, your name will be assigned an InterNIC handle; later registrations will only need your InterNIC handle

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Signing Up for a Domain Name

All of the forms will require at least the following information:

• Domain name (such as course.com)

• Name, address, and e-mail of the registrant

• Name, address, and e-mail of the administrative contact

• Name, address, and e-mail of the technical contact

• Name, address, and e-mail of the billing contact

• Name and IP address of the primary and secondary DNS servers (the routing servers

• Billing information for online payment

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Domain Name Service Servers (DNS Servers)

Because a network server can host more than one Web server, the network server needs a means to identify the Web servers on the network

The Domain Name Server (DNS) is a network service that translates domain names to IP addresses

When you register your domain, you do not provide the IP address for your Web site

Instead, you provide the name and IP address of a DNS server

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Domain Name Service Servers (DNS Servers)

The DNS server contains a listing of domain names and their associated IP addresses

The ISP that hosts your Web site will enter your domain name and IP address in their DNS server

When a client requests a Web page, for example, by entering a URL, the client’s network server locates the relevant DNS server, which then provides the relevant IP address

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The Whois Utility

To locate the DNS servers, InterNIC handle, or registrant information for a Web site, you can use the whois utility

The whois utility looks up the information associated with individuals, domain names, and DNS servers in the registry

To locate the registrant, InterNIC handle, and DNS servers of a Web site using the whois utility, follow the instructions on page 13

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The Whois Utility 1

The World Wide Web Service

A network server is a network software application that provides network-related services such as e-mail, database, messaging, file, and printing services

The network software that stores Web pages and processes the requests for Web pages is called the Web server (sometimes also called the World Wide Web (WWW) Service)

Network administrators can define many Web sites on the same server, and these Web sites are known as virtual Web servers

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The World Wide Web Service

Companies that provide hosting services are called hosting service providers (HSPs)

Some HSPs allow you to have subwebs

Subwebs are subdirectories of a Web site

Internet programming has been referred to as client/server programming because the client application is communicating with the server application

The client communicates with the rest of the Internet via a network server

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The World Wide Web Service

In many instances, the network server is the ISP’s server

The client’s network server routes the request packet to the Web server that contains your Web page

The network server routes the packets back to the client’s browser

The browser receives and processes the request and renders (or displays) the requested Web document

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The World Wide Web Service

Internet applications are no longer limited to a single server

E-commerce Internet applications often communicate with database servers that are not located on the same physical network server as the Web server

In addition to client/server programming, servers communicate with other servers

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Client/Server Programming Using a Web Browser

and a Web Server

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Web Servers

Although there are many different types of Web servers, the most common are Apache and Internet Information Server

When working on desktop Windows computers running Windows 98, developers often use Microsoft Personal Web Server to create a Web environment for testing while they are building their Web sites

The Netcraft Web site at http://www.netcraft.co.uk/ Survey/whats/ offers a utility that can detect the type of Web server and operating system a Web site is using

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Hosting Service Providers

After you have selected a domain name and registered it with one of the InterNIC registrars, you will need a service provider to host your Web site

A hosting service provider (HSP) is an ISP that specializes in Web site hosting

HSPs are also called Web presence providers

Some HSPs specialize in working with Internet programmers, while others provide only general Web hosting services

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Hosting Service Providers

Some HSPs offer collocation, whereby they will maintain the equipment connecting the server to the Internet, but the responsibility for maintaining the server software remains with the company

The person who maintains the Web server is called the Webmaster; in small companies where there is no Webmaster, an Internet programmer is often given responsibility for the maintenance of the Web server

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Hosting Criteria

Before searching for an HSP, determine what criteria you will use to evaluate them

Some Web sites on the Internet allow you to search for the features that HSPs often provide

Compiling an evaluation criteria check list will help you find the right HSP for your needs

Some of the questions that will help you evaluate an HSP are listed on pages 16 to 18 of the textbook

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Locating a Hosting Service Provider

There are several lists of HSPs on the Internet Many of these lists provide a ranking of HSPs

based on the features they support, or on feedback by their membership

CNET contains an extensive list of hosting service providers at http://webhostlist.com/

The following Web sites contain additional lists of hosting service providers• HostIndex - http://www.hostindex.com/

• TopHosts.com - http://www.tophosts.com/pages/topover.htm

• The List - http://thelist.internet.com/

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Internet Programming User Groups

Finally, you should ask colleagues for their opinions about your HSP selections

How have other Internet programmers evaluated this HSP?

While an HSP may claim to have 24-hour availability, you might in fact find that they have been prone to network slowdowns and outages

If you do not know any Internet programmers, there are many user groups that can help

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Creating a Web Page

Web pages are created using the HTML language that was established by the HTML protocol

Web pages can be created in a simple text

editor program such as Notepad, vi, or

BBEdit, or in a Web page editor such as

FrontPage or Dreamweaver

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Web Development Tools

In the early days of the Internet, companies usually created disconnected static Web pages; often recreations of their advertising and print materials

Web tools such as HotDog and HTMLPro offered programmers a graphical user interface for creating HTML code

However, as Internet technologies evolved, companies wanted to add interactivity to their pages

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Web Development Tools

To create these more complex Web pages, developers started using Web page editors and Web site management tools to create and maintain Web sites

Some of the common Web development tools are:• Microsoft Visual InterDev

• Microsoft FrontPage

• Adobe PageMill

• Allaire HomeSite

• Macromedia

• Bare Bones BBEdit for Macintosh

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Web Development Tools

Each of these Web editors can be used to develop small or large Web sites

Most of these vendors also provide additional tools that allow the Internet programmer to create more robust Internet applications

Today, even Microsoft Office allows you to easily create Web pages from within Word, Access, PowerPoint, and Excel

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HTML Tags

HTML is a markup language that uses tags to instruct browsers how to format (or render) the Web page

HTML tags are always enclosed within angle brackets (<>)

Most require a beginning and a closing tag There are two parts to a Web page

• The heading section is identified by a pair of head tags (<head> and </head>)

• The body section is identified by a pair of body tags (<body> and </body>)

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Tags Used in the Heading Section

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Many tags can be used in the heading section of the Web page

Tags Used in the Heading Section

The Title Tag The heading section can contain nested HTML

tags, such as the title tag <title> My Home Page </title>

The Meta Tag The meta tag allows you to provide additional

information about the page that is not visible in the browser <meta name=“variable”content=“value”>

The process of loading a new page into the browser is referred to as client-side redirection

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Tags Used in the Body Section

The body section is identified with a pair of body tags (<body> and </body>)

The body section of a Web page can contain many HTML tags

Some tags are used to format the characters and paragraphs; other are used to insert images, tables, and forms

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Common HTML Body Tags 1

HTML Tab Attributes

Within many HTML tags, you can specify additional attributes

These attributes provide a means of altering the tag in some way

For example, the paragraph tag <p> allows you to insert a paragraph

The align property of the paragraph tag allows you to align the paragraph to left, right, or center or to justify it

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Creating a Basic Web Page Using HTML

The following is an example of a basic Web page named storehome.htm, which was created in Notepad

<html><head>

<title> Store Home </title>

</head>

<body>

<h1> Home Page</h1>

<p><b>Welcome</b> to our store!</p>

</body></html>

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Other HTML Tags

The body tag, which is used to identify the body section, can be modified using several attributes

The image tag is used to insert images

The anchor tag is used to insert hyperlinks to other pages or Web sites

The form tag is used to insert a form

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The Body Tag

The body tag is used to alter the format of the entire document

The body tag contains several attributes

The body tag contains an attribute called bgColor that allows the programmer to change the color of the background

The background property of the body tag can be used to identify a background image for the Web page

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List Tags

Lists can be formatted using the unordered list tag, the ordered list tag, or the definitions list tag

The list items contain nested italic tags, which are used to format the text within the list item tag (as shown at the bottom of page 24 of the textbook)

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Other HTML Tags

The Image Tag

The image tag is used to add a graphic image to the Web page

The Anchor Tag

The anchor tag is most often used to create a hyperlink to another document

You can force the browser to open the Web page in a new window by specifying the target window

The target window can also be identified in the URL

You can use the anchor tag to create a bookmark, which is used to specify a location, within a Web page

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Attributes of the Image Tag 1

The Table Tag

The table tag is used to create a table on a Web page The border property of the table tag is used to create a

border around all of the cells in the table The width property of the table tag can be used to

specify the width of the table either in pixels or by percentage of the browser window

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The Form Tag

Forms are used to receive information from the user

Forms are commonly used to allow users to register on a Web site, to log in to a Web site, to order a product, and to send feedback

The action attribute identifies the program or script that will process the form

The method attribute of the form tag is used to identify how the form field names and values will be sent to the server

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Form-Related Tags 1

The Input Tag Attributes

The input tag creates a form element that can retrieve information

The type attribute identifies the format of the input tag

The value attribute provides a default value for the input tag

Additional attributes are available with the various types of input elements

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Additional Resources

Additional Internet resources, which

include online tutorials that cover HTML

tags and their properties, can be found at

Life Beyond Yahoo

(http://www.lifebeyondyahoo.com/) at

http://www.lifebeyondyahoo.com/life/html.

asp

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Publishing Your Web Page

Some Web development tools, including FrontPage, InterDev, and Dreamweaver, allow you to publish Web pages directly to a Web server

However, if you are using a text editor, you will need a program to copy your files to the Web server

You can use FTP software to transfer your files from your client computer to the Web server

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Summary

The early Internet was called ARPANET and was used by the government and universities for research and education

The Internet uses TCP/IP to route and deliver packets from one computer to another

The ping utility tests network connectivity

The tracert utility can detect whether a Web site is slow, or disconnected from the Internet

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Summary

You can create Web pages using text editors or Web page editors

HTML documents consists of a heading section and a body section, identified by the head and body tags

Personal Web Server (PWS) is available free from Microsoft and allows you to develop and test your Web pages locally

There are many resources available online for learning how to create basic Web pages using HTML

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