1. The Client Server Model

2. ASP.NET Web Forms
One of a number of technologies for web application development
Hides the complexity from the developer
The problem is we need to know how the presentation layer works if we are to use it properly
There are lots of other questions to consider
Client server model
Security
Wider implications

3. The Projector Screen “Model”
Where is the film actually generated?
The projector may be seen as the server
The screen may be seen as the client

4. The Client Server Model
We use web sites to buy goods and services
The page is generated by the server not the browser

5. The Client Server Model
The browser sends data over the network to the server asking for the home page of the site
The server looks for the page
The page might be a static web page; a page generated by code or in many cases a combination of the two
Once the page has been generated the server sends the page to the requesting browser over the network
Once received the browser renders the page to show you the page you asked for

6. Extending the Model Server side code – runs on server (e.g. ASP, PHP)
Client side code – runs in the browser (Java Script)

7. Database Processing Code may exist at.. Server Client
Middle layer etc.

8. Viewed in Visual Studio

9. Where is the Server in Visual Studio?
Follows the client server model
Client browser clearly visible
So where is the server?

10. The Answer… Look in the Windows task bar…
When using Visual Studio the single computer is acting as both client and server…

11. Visual Studio Development
You press F5 to run your program
Visual Studio launches both local browser (client) and local development server
Your browser then communicates with the local server in exactly the same manner as before…

12. The Internet and TCP/IP
Allows programs to talk to each other
Huge network of interconnected computers
Protocol called TCP/IP (Transmission Control Protocol / Internet Protocol)
A network of networks
Each machine allocated an IP address
E.g.
Humans very bad at remembering numbers

13. Domain Name System (DNS)

14. Ports TCP/IP allows programs to talk to each other
The IP address identifies the machine
The port identifies the application to use on that machine
Rather like a phone number for a large organisation with internal extension numbers
No “law” that states which ports are used for what application/service
80 HTTP (web pages)
21 FTP (File transfers)
119 NNTP (Network News Transfer Protocol)
443 HTTPS (secure web pages)

15. The World Wide Web
Internet was fine without the web up until around 1989
File Transfer Protocol (FTP) was used if you wanted to share a file
Telnet was used to log in remotely to control another machine
Usenet was used to share information via news groups (one of the oldest parts of the internet!)
People sometimes incorrectly assume the Web is the Internet!

16. Implications of the Model
Technical
Economic
Social/Political
Security

17. Technical Implications
HTML 5
CSS
Mark-up
Network technologies
Hardware
Browsers
Servers

18. Economic Who is the 80th wealthiest person in the world?
Started by developing a “city guide” sold PayPal for $165 million
Who uses Amazon, eBay etc.?

19. Social/Political
Who is this man?

20. Security What is the latest security breach?