Transcript ECMM6018 Tutorial7

ECMM6018
Enterprise Networking for Electronic
Commerce
Tutorial 7
CGI/Perl and Cookies
Cookies
Definition: Information put on your computer’s
hard disk by a website in the form of text files so
that the website can remember the user at a later
date
 Cookies can be used to store information such as
usernames, passwords or even send current
weather and news for your particular region. In
other words cookies can be used to help make
more customizable web pages.
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Cookies
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Can be used for purposes such as shopping carts
(E-Commerce).
 They can be written in a variety of languages
including PERL, JavaScript, ASP, Cold Fusion
and PHP.
 Examples of sites that use cookies are Amazon,
Payless
Cookies
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Only the Internet site that placed the cookie on
your machine can read it
They are not programs
Specification of cookies
1.A cookie may be no larger than 4k.
2.There may be no more than 20 cookies per
domain.
3.There may be no more than 300 cookies total
from all sources.
Stored under the cookie directory in windows, if
using MSIE
Stored in the cookies.txt file, if using Netscape
Cookies
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6 parameters can be passed to it
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1. The name of the cookie (mandatory)
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2. The value of the cookie (mandatory)
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3. The expiration date of the cookie - if blank it
will expire when the user closes the browser
Cookies – Parameters ctd
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4. The path the cookie is valid for.
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5. The domain the cookie is valid for
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6. The need for a secure connection to exist to use the
cookie.
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The pieces of information are stored as name-value pairs
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Each name-value pair is separated by a semi-colon
How it all works
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The URL of a Web site is entered into the browser,
the browser sends a request to the Web site for the
page. Your browser will contact Web site’s server
and request its home page
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When the browser does this, it will look on your
machine for a cookie file that the Web site has set.
If it finds an the Web site’s cookie file, the browser
will send all of the name-value pairs in the file to
the Web site’s server along with the URL. If it finds
no cookie file, it will send no cookie data.
How It Works - ctd
The Web site’s Web server receives the cookie
data and the request for a page. If name-value
pairs are received, the Web site can use them
 If no name-value pairs are received, the Web site
knows that you have not visited before. The server
creates a new ID for you in the Web site’s database
and then sends name-value pairs to your machine
in the header for the Web page it sends. Your
machine stores the name-value pairs on your hard
disk.
 The Web server can change name-value pairs or
add new pairs whenever you visit the site and
request a page.
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Example
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Cookie being sent from the server to the browser
Content-type: text/html
Set-Cookie: foo=bar; path=/; expires Mon, 09Dec-2002 13:46:00 GMT
 Cookie being sent from the browser to the server
Content-type: text/html
Cookie: foo=bar
Perl and Cookies
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CGI scripts create one or more cookies and send
them to the browser in the HTTP header.
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Browser returns the cookies to the CGI script
during subsequent interactions
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Interface to cookies by using the cookie method()
Cookie Method
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Create an object of type CGI and assign it to a variable
E.g.
$cgiobject=new CGI;
$cookie = $cgiobject->cookie(-name=>'sessionID',
-value=>\%cookie_data,
-expires=>'+1h',
-path=>'/cgi-bin/database',
-domain=>'.capricorn.org',
-secure=>1);
Sending Cookies through
HTTP
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The cookie created by cookie() method must be
incorporated into the HTTP header
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E.g. print $cgiobject->header(-cookie=>$cookie);
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It is possible to send multiple cookies in the HTTP
header
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print $cgiobject->header(cookie=>[$cookie1,$cookie2]);
Retrieving Cookies
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To retrieve a cookie, request it by name by calling cookie()
method with the name parameter
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E.g. cookie_data=$cgiobject->cookie(“sessionID");
Useful Links
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http://stein.cshl.org/WWW/software/CGI/cgi_docs.html#cookies
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http://www.cookiecentral.com
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http://www.katsueydesignworks.com/cgi_cookies.htm