The Module Road Map

Assignment 1 Road Map

We will look at… Internet / World Wide Web Aspects of their operation The role of clients and servers ASPX Page (Web Form) How it is passed between browser and server The structure of the page How it provides functionality to the browser

Credit Categories Assignment 1 Credit Category 2 Assignment 2 Credit Category 2 & 3 Assignment 3 Credit Category 1

The Internet and TCP/IP Network of networks Defence research in the 60s TCP/IP (Transmission Control Protocol / Internet Protocol) Allows programs on computers to talk to each other

The IP Address Uniquely identifies each machine 32 bit number made up of four 8 bit numbers Visit Assigned in blocks G677 (my server)

Name Servers not obviously

Ports TCP/IP allows programs on machines to communicate IP address identifies machine port number identifies program There is no law that states a specific port must be used for a service however there are certain ports that traditionally provide services. 80 HTTP (web pages) 21 FTP (File transfers) 119 NNTP (Network News Transfer Protocol) 443 HTTPS (secure web pages)

The World Wide Web Up until about 1989 the Internet existed quite happily without the World Wide Web File Transfer Protocol (FTP) Telnet Usenet World Wide Web - Internet

The Client Server Model

Server v Client Side Code Code may be added at either end of the process Client side code runs at browser Action Script (Flash) JavaScript VBScript Server Side Code ASP.NET (C #) PHP JSP

New Process to Consider

XHTML Forms GET and POST Simple web form (linked from the module web site)

XHTML Form Code Change POST to GET

Active Server Pages (ASPX) Events User or System Generated User triggered events ClickTriggered when a user presses a button Selected Index ChangedActivated when the user selects an item off a drop down list System generated LoadRuns when the ASPX page is loaded by the server Typically used to initialise the web form UnloadRuns when the ASPX page is unloaded from the server Typically used to save data Handled by event procedures

Anatomy of an ASPX Page

Code may be Embedded in the Web Form

Active Server Controls Note the tag <asp

Visual Designer

Post Back = False Post back is false on the first HTTP request The browser sends the request to the server The server begins processing the page The server executes any code associated with the page load event The server runs any code in the page unload event All asp controls are processed by the server and changed into suitable XHTML controls This produces XHTML built from the ASPX page The XHTML is sent to the requesting browser

What the Browser Gets… Not the ASPX page but XHTML

Post Back = True The browser sends the request to the server The server begins processing the ASPX page The server executes any code associated with the page load event The server executes any code associated with any events triggered (in this case the click event of the Go button) The server runs any code in the page unload event All asp controls are processed by the server and changed into suitable XHTML controls (They will be updated with any data from the XHTML version of the form) This produces XHTML built from the ASPX page The XHTML is sent back to the requesting browser

Visual Studio Development Server Visual Studio starts the development server VS then launches the browser with the URL Visual Studio makes your computer “talk to itself”