Internet Concepts

WEB PROGRAMMING
Introduction
What is the web?
Its a whole bunch of interconnected computers
communicating to one another.
 The computers (on the web) are connected

by phone lines, digital satellite signals,
cables, and other types of data-transfer
mechanisms.
 A 'data-transfer mechanism' is a way to move

information from point A to point B to point C and so
on.
Web Programming 1
World Wide Web (WWW)
 Its a system of Internet servers that
supports hypertext and multimedia to
access several Internet protocols on a
single interface.
 for the Web to be accessible, certain
agreed-upon standards must be followed to
create and deliver its content.
 World Wide Web Consortium (W3C) is an
organization that standardizes the Web
Web Programming 2
Protocols of the Web;(services)
 internet protocols are sets of rules
that allow for inter-machine
communication on the Internet.
 a few of the protocols you can
experience on the Web includes:
 HTTP (HyperText Transfer Protocol):

transmits hypertext over networks.
 This is the protocol of the Web.
Web Programming 3
Web protocols
 E-mail(SMTP)
 (Simple Mail Transport Protocol or SMTP):
distributes e-mail messages and attached
files to one or more electronic mailboxes
 FTP (File Transfer Protocol):

transfers files between an FTP server and
a computer, for example, to download
software
Web Programming 4
Web protocols..
 VoIP
(Voice over Internet Protocol): allows delivery of
voice communications over IP networks, for
example, phone calls.
 chat:
Allows you to combine text with graphics while
participating in a real-time conversation with 2 or
more people in the internet
 News;
Hosts electronic discussion groups through which
participants share information and opinions
Web Programming 5
Web protocols..
 FTP;
File Transfer Protocol is used to
transfer files between 2 computers on
TCP/IP network
 Telnet;
offers a way to log on to and work from
another computer
 Users can access internet services that they
may not have on their own computers
Web Programming 6
Resource addresses
 URL and Domain Name System
 URL stands for Uniform Resource Locator.
 URL specifies the Internet address of a file stored on
a host computer, or server, connected to the
Internet.
 Web browsers use the URL to retrieve the file from
the server.
 This file is downloaded to the user's computer, or
client, and displayed on the monitor connected to
the machine.
 Because of this relationship between clients and
servers, the Web is a client-server network
Web Programming 7
DNS
 Domain Name System (DNS) is a worldwide system of
servers that stores location pointers to Web sites.
 The numeric address, called the IP (internet protocol)

address, is actually the "real" URL.
 Since numeric strings are difficult for humans to use,

alphanumeric addresses are employed by end users.
 URLs are translated into numeric addresses using DNS
 After translation by the DNS, the browser can contact

the Web server and ask for a specific file located on its
site
Web Programming 8
Anatomy of a URL
 This is the format of the URL:

 protocol://host/path/filename
 For example,
http://www.senate.gov/general/capcam
.htm
 This URL is typical of addresses hosted
in domains in the United States.
 The structure of this URL is shown
below.
Web Programming 9
Structure of URL
1. Protocol: http
2. Host computer name: www
3. Second-level domain name: senate
4. Top-level domain name: gov
5. Directory name: general
6. File name: capcam.htm
Web Programming 10
TLDs
 Note how much information about the
content of the file is present in this
well-constructed URL.
 Several top-level domains (TLDs) are
in common use such as:
 .com
 .edu
 .org
 .co.uk
Web Programming 11
server
Servers are computers with a special software
installed called 'server' software.
function of server software / programs?

 to 'serve' web pages and web sites.
 Basically, the server computer has a bunch of web

sites loaded on it and it just waits for people (via
web browsers) to request or ask for a particular
page.
 When the browser requests a page the server sends

it out
Web Programming 12
finding a web site by web server
 Done by typing in the URL, or, the web

site address. So for example, if you
wanted to find the web site
www.killersites.com, you would type in
the address into your web browser's
address bar
Web Programming 13

Internet Concepts

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WEB PROGRAMMING

 The computers (on the web) are connected

 A 'data-transfer mechanism' is a way to move

 HTTP (HyperText Transfer Protocol):

 FTP (File Transfer Protocol):

 The numeric address, called the IP (internet protocol)

 Since numeric strings are difficult for humans to use,

 URLs are translated into numeric addresses using DNS

 After translation by the DNS, the browser can contact

 This is the format of the URL:

function of server software / programs?

 Basically, the server computer has a bunch of web

 When the browser requests a page the server sends

 Done by typing in the URL, or, the web

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