the internet and the world wide web internet programming using vbscript and javascript 1
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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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