Spider Course Day 1

INTRODUCTION TO WEBSpider Web Weaving Course.

Day 1

Harishankaran K

HTTP

Hypertext Transfer Protocol HTTP is a request/response protocol between

a client and a server. The client making an HTTP request—such as

a web browser, spider, or other end-user tool—is referred to as the user agent.

The responding server—which stores or creates resources such as HTML files and images—is called the origin server.

In between the user agent and origin server may be several intermediaries, such as proxies, gateways, and tunnels.

REQUEST/RESPONSE PROTOCOL

The client sends the request. The server sends a response according to the

request from the client.


The client sends a HTTP request. The server receives the request. Server may do some processing according to

the request sent. It returns HTTP response.


WEB SERVER

Program that accepts HTTP requests from the client, and provides an HTTP response to the client.

The HTTP response usually consists of an HTML document, but can also be a raw file, an image, or some other type of document.

Examples are Apache, Microsoft IIS, Google GFE, lighthttpd etc.

WEB BROWSER

Web browsers communicate with Web servers primarily using HTTP to fetch web pages.

Examples are Firefox, Opera, Internet Explorer, Elinks, Safari etc

Web browsers format HTML information for display, so the appearance of a Web page may differ between browsers.

SPIDER

A program or automated script which browses the World Wide Web in a methodical, automated manner.

Other names are web crawler, ants, automatic indexers, bots, and worms.

Web crawlers are mainly used to create a copy of all the visited pages for later processing by a search engine that will index the downloaded pages to provide fast searches.

HTTP REQUEST

GET /course/ HTTP/1.1 Host: spider User-Agent: Mozilla/5.0 (X11; U; Linux i686;

en-US; rv:1.8.1.4) Gecko/20070603 Fedora/2.0.0.4-2.fc7 Firefox/2.0.0.4

Accept: text/html Accept-Language: en-us,en Accept-Encoding: gzip,deflate Accept-Charset: ISO-8859-1,utf-8 Keep-Alive: 300 Connection: keep-alive

HTTP RESPONSE

HTTP/1.x 200 OK Date: Mon, 04 Feb 2008 03:58:24 GMT Server: Apache/2.2.0 (Fedora) X-Powered-By: PHP/5.2.2 Content-Length: 2742 Connection: close Content-Type: text/html; charset=UTF-8

HTTP STATUS CODES

1** Informational 2** Success 3** Redirection 4** Client Error 5** Server Error

200 – OK 403 – Forbidden 404 – Not Found 500 – Internal Server Error

SCRIPTING LANGUAGES

Web browser should support the scripting languages.

Apache supports php, python, and many other languages.

Web server executes the php file in the server to produce dynamic HTML content.

Examples are PHP, Python, Ruby, Perl etc…

DATABASE SERVER

Data Base Management System is used to store the data.

Most scripting languages have inbuilt API support to connect to the database server and process the data.

The database server can be a separate server or can run in the same server.

Example are MySQL, MSSQL, PostgreSQL

WEB MODEL

LAMP

WAMP

Role Name

Operating System Linux

Web server Apache

Database MySQL

Scripting Language PHP

Role Name

Operating System Windows

Web server Apache

Database MySQL

Scripting Language PHP

LAMP

HTTP SESSION STATE

HTTP is a stateless protocol. The advantage of a stateless protocol is that

hosts do not need to retain information about users between requests, but this forces web developers to use alternative methods for maintaining users' states.

A common method for solving this problem involves sending and requesting cookies.

STATELESS HTTP

COOKIE

INTRODUCTION TO UNIFORM SERVERSpider Web Weaving Course.

Day 1

Harishankaran K

STEPS

Download Uniserver from the URL mentioned.

Extract the file. Start the server using Server_start file in

the Uniserver folder. Add the files under W:/www folder. Stop the server using Stop file

SAMPLE FILES

Index.html <html> <head><title>Hello</title></head> <body> Ha ha ha. He he he. Hoo hoo hoo. My first

web page is ready. :). </body> </html>

SAMPLE FILES

index.php <?php echo phpinfo(); ?>

Thank you

Technology

Spider Course Day 1