Web programming

1. Unit-1
Fundamentals of web

2. Contents
• Fundamentals of web:
• Internet, www, web Browsers, web servers,
Urls, MIME, HTTP, Security, the web
programming toolbox.
• XHTML
• Origins and evolution of HTML, XHTML, Basic
syntax, standard XHTML document structure,
Basic text markup images, Hypertext Links,
Lists, Tables.

3. Fundamentals of web
A computer network is a group of two or more computer system
linked together.
Internet: The internet is a global network of networks.
Or
The internet is the largest computer network in the world,
connecting millions of computers.
The first internet was developed by ADVANCE RESEARCH
PROJECT AGENCY [ARPA] of US department of defense in 1969.
It was called as ARPA NET.

4. APPLICATIONS
• Search engine: It can be used to search anything and everything. Most
popular search engines are Google and yahoo searches.
• Shopping: Internet has made shopping very easy and flexible. You can
buy or sell online.
• Communication: It helps people to communicate either with the use of
social networking websites or through e-mails and chats.
• Job search: Nowadays, many people search for their jobs online as it is
quicker and there is a larger variety of job vacancies present.
• Research: Research papers are present online which helps in the
researcher doing a literature review. Video Conferencing: It enables direct
face-to-face communication across networks via web cameras,
microphones, and other communication tools.
• E–commerce (electronic commerce or EC) is the buying and selling of
goods and services, or the transmitting of funds or data, over an
electronic network, primarily the Internet. Largest e-commerce
companies in India are Flip kart, Snap deal, and Amazon India.
• On-line payments
• The rising boom of online payments in India has given way to many new
entrants in the industry such as Paytm, Mobikwik etc who are majorly
wallet driven payment companies.

5. Internet Protocol:
The internet protocol is the language that
computers use to communicate over the internet.
Internet Protocol Address (IP Address):
The Internet protocol address of a machine
connected to the internet is a unique (different) 32 bit
number.
They are usually written as 32 bit numbers
separated by dots (periods).
E.g.: The IP address of www.google.com is
209.85.148.105
The IP address of www.bangaloreuniversity.in is
14.139.159.35

6. Domain Names:
Domain names are textual names given to the nodes on the
internet.
It is in the form of words separated by dots.
E.g.: www.google.com
www.yahoo.org
The last position of domain name represents the top level domain
or first level domain.
There are several hundred top level domain names as follows:
Country code Domain: a unique two-letter combinations for every country
like IN, UK, US
Domain name Assigned To
Com
Edu
Gov
Net
Mil
Commercial education
Educational institution
Government organization
Major network support center
Military group

7. Sub domains:
Sub domains are the third level domains that are used to
organize the web site content in systematic manner.
They are just like folders under the root directory .But they will
have a special URL to access.
Ex: 2nd level domain Top level domain
http://www. kar.nic.in
Sub domain (3rd level domain)
Purpose of sub domains:
1. We can organize the website.
2. We can share our disk space with our friends and family.
Domain Name Server:
Domain name server is a software system that translates a
computers fully qualified domain name in to an IP address.

8. • World Wide Web (WWW/web):
– The web is a system of interlinked hypertext
documents accessed (through) via the internet. It
is developed by Tim-Berners-Lee in 1989 at CERN
(European Laboratory for Practical physics).
• It is the information –sharing model that is built on top
of the internet.
• The web uses HTTP protocol to transmit data over the
Internet.
• The web utilizes browsers like Firefox to access the Web
documents.
NOTE: The Internet is the restaurant, and the Web is
the most popular dish on the menu.

9. • Web Browser:
– It is a software application used to locate & display
WebPages. It is able to retry, find, view and send
information over the internet
Or
– Browsers are the programs running on client
machines. They are called browsers because they
allow the user to browse the resources available on
servers.
• The most commonly used web browsers are:
1. Microsoft Internet Explorer,
2. Mozilla Firefox
3. Google Chrome
4. Apple safari
5. Opera
6. Net-scape Navigator

10. Web Servers:
A web server is software that runs on the website hosting server
computer. Its main purpose is to serve the WebPages; which
means it waits for requests from web browsers and responds by
sending the required data back.
Or
Web servers are programs that provide documents to
requesting browser.
The most commonly used web servers are:
1. Apache HTTP server
2. Microsoft Internet Information Server (MIIS)
Apache HTTP Server:
1. It is the most popular web server on the web since 1996.
2. It was develop and maintained by Apache Software
foundation.
3. Apache is available for a range of OS including UNIX,
LINUX,WINDOWS & Etc.,
4. It is a open source product.

11. • Microsoft Inter Information Server (MIIS)
 It was developed by micro-soft Corporation.
 It works only on windows operating system.
 It is vendor specific & not a open source.
Web Server Operation or the Role of web server on the Internet.
The term web server can be two things.
1. A computer on which a website is hosted &
2. A Program that runs on such a computer.
Browser Connects to a server &
request a web page
The Server sends back the requested page
Client Computer Server

12. • The process of loading the webpage in a web browser begins
with the user by entering the URL of the requested field.
• Then the browser broke the URL into 3 parts.
1. The Protocol (“http”)
2. Server name (www.irctc.co.in)
3. File name
• Then the browser communicates with the domain name
server to translate the server name into IP address. Which the
browser uses to connect to the server.
• The server software now takes up the request & searches for
the requested webpage on its hard disk. On finding the file
the server sends the requested data back to the browser.
• Finally the browser reads the html tags & determines how a
web page is to be displayed on the screen that could be
understood by the user.
• The transfer of data b/w browser & server is governed by http
protocol.

13. URL (Uniform Resource Locator):
• URL is a fancy name for address.
• It contains the information about where a file is & what a
browser should do with it.
• Each file on the internet as a unique URL.
• URL Format or Parts of the URL:
• There are 4 parts in a URL:
1. Scheme:
 It tells the browser how to deal the file that it is about
to open. The scheme is often a communication
protocol.
 The most commonly used scheme for web
communication is http which is used to the web pages.
Scheme: // hostname: port/path-to-document-filename

14. 2. Hostname:
The DNS domain name or IP address of the server where the
requested website is hosted.
3. Port:
The TCP port number which specifies the process that runs on
web server to which the message is to be forwarded for handling.
4. Path-to-document- and file name:
The name & location of the requested resources under the
server document based directory.
Ex: http:// www.site.com:80/liz/file-html
Scheme host-name TCP Port Number Path Filename

15. MIME: (Multipurpose Internet Mail Extension)
– A Browser needs some way of determining the form of a document
that it receives from a web server.
– The types of the documents that are received from the web server by
the browser are specified with the MIME.
– That means a web server attaches a MIME format specification to the
beginning of the document that it is about to send to a browser.
– When the browser receives that document from a web serve it uses
the included MIME format specification to determine what to do with
the document.
• The MIME format specification takes the following:
• Syntax:
• The most common MIME types are
Type / subtype
Type Subtype Example
Text
Images
video
Plain, html
Gif, jpeg
mpeg
Text/html, text/plain
Image/gif, image/jpeg
Video/mpeg

16. HTTP (Hyper Text Transfer Protocol)
 HTTP is the most popular application protocol used in
the internet.
 HTTP is an asymmetric request response client server
protocol.
“Asymmetric means there is a many to one relationship
b/w client & the server”
 HTTP is a stateless protocol.
“A stateless protocol is the one that does not maintain a
relationship between requests. Each request is unrelated to any
previous request."
The Communication using HTTP involves 2 phases:
1. The Request phase:
Where the client sends a request message to the server.
2. The Response phase:
Where the server returns a response message to the client request.

17. An HTTP message consists of 3 main parts.
1. Message head
2. Blank line
3. Message body (Optional)
• HTTP Request Message:
Format: Request-message-header
Blank line
(Optional)
1. The first line of the header is the request line followed by request headers.
The syntax of request line is:
Request line
Request headers
Request message
Body
Request-method-name request-URI HTTP-Version

18. • Request-method-name:
HTTP Protocol provides a set of methods (get, post, head, and
delete, put). The client can use one of these methods to send a
request to the server.
• HTTP request methods:
HTTP protocol defines a set of request methods which can be
used by the client to send request messages to HTTP server.
• GET: A client can use the get method to request a web resource
from the server.
• HEAD: A client can use the head method to get the header
information of the specified document.
• POST: Post is used to post the data up to the web server. PUT: Ask
the server to store the data.
• DELETE: Ask the server to delete the data.
• TRACE: Ask the server to return a diagnostic trace of the actions
its take.
• OPTIONS: Ask the server to return the list of request methods its
supports.

19. Request-URI:
It specifies the address of the requested file. HTTP-Version:
Two versions are currently used: HTTP/1.0 and HTTP/1.1
E.g.: Get/test.html HTTP/1.0
Head/query.html HTTP/1.1
2. The request headers are in the form of name: Value pairs
Syntax:
E.g.: Host: www.xyz.com
Connection: keep-alive
Accept: image/gif
Accept-language: us-en
Note: The most common request-header name is the accept
which specifies the type of the document that the browser
is willing to accept from the server.
Request-header-name: request-header-value

20. HTTP response Message:
• The format of HTTP response message
Response message heads
Separated by blank line
(Optional)
1. The first line is called the status line followed by optional headers.
The syntax of status line is as follows:
HTTP-Version: The HTTP version used in this session either HTTP/1.0 or HTTP/1.1
Status-code: A 3 digit number generated by the server to reflect the outcome of
the request.
Reason-phrase: It gives the short explanation to the status code
Status line
Response headers
Response
Message body
HTTP-version Status-code reason-phrase

21. • Examples of the Status-code:
1. HTTP/1.1 200 Ok
2. HTTP/1.0 404 Not Found
3. HTTP/1.1 500 Internal Server Errors.
2. The Response headers are in the form of Name: value pair
Syntax:
• Examples of response headers:
Content-type: text/html
Content-length: 35
Connection: keep-alive
• Note: The common & only essential field is the content line. This
contains the information about the type of the document
Response –header-name: response-header-value

22. Security: Security is the most crucial issue for Internet.
The most common security issues are,
1. Privacy
2. Authentication
3. Integrity
4. Non-Repudiation
Privacy: There should be privacy for the client data.
Authentication: All the data which is residing either in client or server must be used by
authenticated person only.
Integrity: The personal data stored on the server like credit card no. or password
should not be modified by third party.
Non-Repudiation: It must be possible to legally provide that the message was actually
send and received.
The Data Encryption & decryption are the most commonly used technique for
ensuring all the security issues:
Encryption: Encryption is a technique by which the information send over the
network is converted into another form so that no one can understand this
information.
Decryption: The technique by which the encrypted methods message is decoded
back to its Original message is called Decryption.