The Client Server Model ASP NET Web Forms

The Client Server Model

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

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

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

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

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

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

Viewed in Visual Studio Data Layer Middle Layer Presentation Layer

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

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

Visual Studio Development You press F 5 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…

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. http: //209. 85. 227. 105/ Humans very bad at remembering numbers

Domain Name System (DNS)

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)

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!

Implications of the Model Technical Economic Social/Political Security

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

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

Social/Political Who is this man?

Security What is the latest security breach?