Server-side Scripting, Exams of System Programming

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Server-side Scripting

Slides courtesy of Xenia Mountrouidou

URLs and web servers 

Usually when you type a URL in your browser:^ 

Your computer looks up the server's IP address usingDNS

Your browser connects to that IP address and requeststhe given file

The web server software (e.g. Apache) grabs that filefrom the server's local file system

The server sends back its contents to you

2

http://server/path/file

URLs and web servers (cont.) 

Some URLs actually specify programs that the webserver should

run

, and then send their output back

to you as the result:^ 

The above URL tells the server

facebook.com

to run the

program

home.php

and send back its output

4

http://

www.facebook.com/home.php

Server-Side vs. Client-Side What are they and what are their differences? Scripting Languages

By Lories Slockbower

Types of Scripting Languages 

Server-side Scripting Language^ 

Can use huge resources of the server  Complete all processing in the server and send plain pages to the client  Reduces client-side computation overhead 

Client-side Scripting Language^ 

Does not involve server processing  Complete application is downloaded to the client browser  Client browser executes it locally  Are normally used to add functionality to web pages e.g. different menustyles, graphic displays or dynamic advertisements

Different Scripting Languages 

Active Server Pages (ASP)^ 

Server side scripting language

Developed by Microsoft

Good at connecting to Microsoft databases

Runs only on Microsoft servers

Perl^ 

Old UNIX language

Found on all Windows and Linux servers

Can handle text manipulation tasks

Excellent web scripting language

Different Scripting Languages 

CGI (Common Gateway Interface)^ 

Server-side solution  Needs to launch separate instance of application for each web request  Allows direct interaction with users 

ASP.NET^ 

Server-side technology to create faster, reliable and dynamic webpages  Supports .NET framework languages (C#, VB.NET, JScript.NET)  Provides flexibility to designers and developers to work separately

Different Scripting Languages 

VBScript^ 

Microsoft’s scripting language  Client side Scripting language  Very easy to learn  Includes the functionality of Visual Basic 

JavaScript^ 

Client-side Scripting language  Easy to use programming language  Enhance dynamics and interactive features of a web page  Allows to perform calculation, write interactive games, add specialeffects, customize graphic selections, create security passwords

What is server-side scripting?

Server-side scripting is amethod of programmingfor the web that runssoftware on the serverrather than the browseror installed plugins tocreate dynamic webpages.

Server-Side Scripting 

Server-side pages are programs written using oneof many web programming languages/frameworks^ 

examples: PHP, Java/JSP, Ruby on Rails, ASP.NET,Python, Perl

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Advantages of server-side scripting



User does not need to downloadplugins like Java or Flash



User can create one template forthe entire website



The site can use a contentmanagement system which makesediting simpler.



Generally quicker to load thanclient-side scripting



User is able to include external filesto save coding



Scripts are hidden from view so it’smore secure. Users only see theHTML output.

Disadvantages of server-sidescripting



The scripts can be used byattackers to access the server.They do this by changing theURL to something that takesadvantage of a hole insecurity. System administratorsmust keep all server-sidescripting updated and use anapplication firewall to preventthis.



Scripting software must beinstalled on the contentmanagement system tools inorder to store the dynamicdata.

What is client-side scriptinglanguage?



Client-side scripts

are placed within

an HTML document in the user’s webbrowser rather than the web serverto allow greater interactivity in adocument.

For example – client-side

scripting could check the user’s formfor errors before submitting it



Enables web pages to changecontent according to user input andother variables, including the time ofday. Can also be stored in aseparate file that is referenced tothe documents that use it.

How does it work? 

Usually, JavaScript codestarts with the tag <scriptlanguage="JavaScript">and ends with the tag.

Files are first sent to theuser’s computer by theweb server which executesthe script and displays thedocument.

The client-side script mayalso include browserdirections based oncertain user functions suchas clicking buttons.

Frequently, you can seethe the source card byviewing the file thatcontains the script.