COMP2121 Internet Technology Richard Henson University of Worcester March 2011

Week 8 – Introduction to Server-Scripting n Objectives of Session  Explain the limitations of client- scripting  Analyse a network infrastructure and server platform to assess possibilities for using server scripting  Implement server scripting across an Intranet and through the Internet

Client-Server Systems n Server end:   access control to the network and its resources controlled by logon service   access to resources depends on user rights – assessed by logon data n Client-end:   user who wishes to access network resources server client

Requests and responses Client requests information Server processes the request, sends a response back to the client

Bandwidth and Client/Server processes n Messages transferred between client and server via network

Bandwidth and Client/Server processes n Data transfer: the faster the better…  most effective on LANs - nowadays 1000 Mbits/sec or more  between connected Internet computers bandwidth needs to be as high as possible - 2 Mbits/sec upwards n Slow connections…  data takes longer to get through  so longer time to get a response back  server could even “time out”

More about HTTP and Client- Server Computing n Client and server systems work right up to the application layer n To allow client-server interaction on the web, Tim Berners-Lee designed HTTP to integrate well with his basic web page formatting language - HTML  HTML language GET command instructs the client process to get data for the server  HTML POST command sends client data either using an protocol or using HTTP

Web Dynamic Client-Server Model I n a typical web- based client-server application: 1.The HTML form displayed on a web browser at the client end collects data 2.Using HTTP the form data is sent to a web server

Web Dynamic Client-Server Model  The web server processes the data according to instructions on a specified server script  Using HTTP, the results of processing generated as specified by the script are sent back to the client  The web browser on the client machine displays the results on a web page in a specified position

Web Dynamic Client-Server model n All this gets even more complex when a database, and database programming, are also involved at the server end…

Server-scripting and dynamic pages on The Web n The following apply to ALL types of scripting used on the web…  scripts need to use real programming code »note: HTML is a FORMATTING language, NOT a programming language  both client and server ends have programming code: »client end…embedded within a HTML page »server end… could be embedded or separate

Languages used for Server Scripting n Much has been tried since w3c launched HTML as an interactive language in the early 1990s…  use of an existing language in a completely separate file, which is already compiled and ready to go: »the original approach:.cgi »any language could in theory be used »in practice “C” was usually favoured  use of an existing language embedded in a HTML file »The Microsoft.asp approach, using embedded VB source code »The Sun.jsp approach, using embedded Java (Script) source  Invention of new scripting languages that are “HTML-like” and easily embed with HTML »Cold Fusion.cf »Preprocessor Hypertext processing.php

Microsoft’s first attempt at server scripting… n In 1996, Microsoft introduced active server pages (asp)  hugely successful (VB very popular…)  soon became more popular than.cgi n However, in spite of the great success of asp, big problems were emerging…  by 2000, hackers were attacking Microsoft servers and finding many security holes in IIS »Microsoft only coped by offering hotfixes  further problem: use of VB source code »if server not secure, code could be copied or compromised »Scripts could not be truly “object oriented”

Alternative Scripting Lanuguages using the embedded approach n JSP n PHP n PERL n Cold Fusion

JSPs (Java Script Pages) n n Produced by Sun Microsystems   extension of the Java TM Servlet technologyJava TM Servlet technology n n According to Sun, Servlets:   “fit seamlessly into a Web server framework and can be used to extend the capabilities of a Web server with minimal overhead, maintenance, and support.” » »platform-independent » »100% pure Java » »enhanced performance » »separation of logic from display » »ease of administration » »extensibility into the enterprise

PERL n Invented by Larry Wall in 1987 n Became popular as a web programming language in the late 1990s n Features of C but an interpreted language (like Java) n Not for programming novices…

Evolution into PHP Evolution into PHP (Hypertext Pre-processor) Started as just a collection of PERL scripts in 1995 Started as just a collection of “ free” PERL scripts in 1995  became popular as a rival to the asp approach for programming code embedded in HTML  then became very popular as Microsoft wrestled with asp -> asp.net n Open source and integrates well with open source databases  e.g. MySQL

PHP scripts n n Originally designed for Linux-based systems   executed on a type of web server called Apache n n Can now run happily on IIS   now getting very popular with non-Linux platforms n n Big improvements in performance with PHP v4 n n XML functionality with v5 (released 2005) n n Can download the environment directly from the PHP website:     XAMPP provides MySQL and Apache webserver environment

Cold Fusion n n Originally produced by Altair with its own scripting language (CFML) for the Microsoft platform   arguably easier to use than asp n n Purchased by Macromedia in 2003 (Dreamweaver, Flash, Director, etc.)   Dreamweaver has good support for Cold Fusion scripting n n Now also available for the Java environment n n Macromedia itself now part of Adobe

ASP becomes ASP.NET n Microsoft’s new approach to server scripting for the new millennium…  building on asp principles  new system that used “intermediate language”, rather than source code on the server  much more difficult to hack n Problem was… they had to scrap the.asp environment, and adopt a new architecture…  known as the.net framework  as many developers were accustomed to.asp this took awhile to catch on!  many people still confuse asp and asp.net…

Evolution of.net framework (2001) n Version 1.1  intermediate language  run-time environment for scripts »compiled code can’t easily be hacked  Programming Code can be separated from HTML; »as with cgi… »but without degradation in performance  Web controls introduced by drag-and-drop for ease of development  XML can replace HTML code…

Evolution of.net framework (2005) n Version 2.0  more and better controls  some Integration with Active Directory  Visual Web Developer 2005 introduced »based on Visual Studio n user friendly development environment »easy use of master pages and CSS »simulated web server for ease of testing

Evolution of.net framework (2008, 2010) n Version 3.5  further enhancement to controls  greater integration with Active Directory  Visual Web Developer 2008 provided more controls, more wizards, and better formatting tools n Version 4.0  as above. Generally regarded as easier to use than VWD 2008

PHPs & asp.net today n n PHPs attractive for serious programmers who dislike the Microsoft approach…   integration of cut-and-paste code still needs an environment like Dreamweaver n n Industry view (post-millenium)   Unix-based Servers running PHPs considered to be more secure against hackers than Windows 2000/IIS running asp   asp.net running on Windows 2003/IIS v6/7 later accepted as being a very stable platform n n Both widely in use today…

Platforms for Development n n Dreamweaver excellent for asp,.net. php & ColdFusion until Creative Studio n n From CS1 onwards (2005ish):   no support for.net development   solid support for php & Cold Fusion n n Visual Web Developer 2005, 2008, 2010   gradually took away Dreamweaver customers using asp.net

When to use Server Scripting (1) n Whenever programming logic is required that needs to be shared via Internet browsers! n Good for security  if web server properly configured… n And accountability  clients can be forced to log on

When to use Server Scripting (2) n When client end lacks storage & processing power  fits well with the thin client model for web & network computing  very popular for massively multiplayer games n Client just sends the requests and asks the questions  server does the processing and provides the web pages with answers/responses to requests

When to use Server Scripting (3) n Whenever centralised data storage & processing is needed to support activities of a website  essential for security of sensitive data  waste of space and resources to store & process databases locally

(4) Securing of Sensitive Data between Client and Server n Extended Internet infrastructure designed around the webserver model  organisation can get an authentication certificate (SSL certificate), and make it available through their webserver »client can view server certificate  Client can access sensitive data at server end by authenticating themselves (log in)  data encrypted and sent using https protocol

Platforms for developing a website running server-scripts n Computer capable of supporting Windows XP/2003/Vista/7 or an equivalent Unix-based operating system n TCP/IP protocol stack running on server n Web Server software such as:  Internet Information Server  Apache n Broadband connection to the Internet

Typical Infrastructure for putting Server Scripting online n Make sure the internal “client-server” computer network is secure n EITHER use the firewall/proxy server as a router to separate the internal (local) network from the External (i.e. Internet) network nOR, if OSI level 3-4 protocol conversion needed, use a gateway  converts data into appropriate protocol and diverts it between the Internet and the local network  can be used to link networks running different protocols

Putting the Secured network on-line n A digital connection with plenty of bandwidth is needed between the router/gateway and a computer connected to the Internet n Regular monitoring of the network is essential to ensure that unauthorised users are not trying to gain access

Web Hosting and ISPs (Internet Service Providers) n Only the largest corporate enterprises are likely to be part of the Internet n Most businesses need to find a partner who will provide a link between the connection medium and the Internet that meets their needs  Many Internet service providers available  The problem is usually “which to choose”, rather than finding a partner…

Web Hosting n Two possibilities:  ISP provides hosting and web space, organisation manages website  ISP provides hosting AND manages website n ISP will also provide:  the all important IP address that will allow a presence on the Internet  the domain name that will allow other Internet users to find the website

Criteria for choosing a web host (apart from cost!) n Amount of web space? n Bandwidth availability? n Hardware & OS? n Uploading techniques? n Protocols supported? n URL available? n type of server scripts supported? n Site management tools? n Databases supported?

Exercise for Next Week n Search Google for web hosts  How many available?  How could you choose? n Use the following URL to compare web hosts and their offerings: 