s kills : none

Skills: noneConcepts: Web client (browser), Web server, network connection, URL, mobile client, protocol

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Retrieving a Web page

Where does this topic fit?

• Internet concepts– Applications– Technology– Implications

• Internet skills– Application development– Content creation– User skills

The World Wide Web in plain English (2m 46s):http://www.commoncraft.com/world-wide-web

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Client and server

Client Server

Can you name a Web client program? If not, ask someone to explain this question to you.

What happens next?

Uniform resource locator (URL)

Establish a temporary connection

Client Server

Request the page

Client Server

Request

Send the page to the client

Client Server

Request

page

page

Client displays the page

Client Server

Request

page

Drop the connection

Client Server

Request

Data flow

Webserverprogram

Memory

Storage

Requestedpage

Webclientprogram

Memory

Display

Requestedpage

Client ServerRequest

Page

The Internet

What if the requested page is not found?

What does the “page not found” error message at www.google.com look like?

Pages with links

Client Server 1

Server 2

1. Get first page

2. Get second page

Mobile Web clients

1. Establish a temporary connection between the client and server 2. Client sends the request to the server3. Server returns the requested page or an error message4. Client displays whatever the server returns5. Disconnect – drop the connection

Client Server

request

page

Summary: retrieving a Web page

1. What happens if the user accidentally misspells the URL?

2. Can a server be handling requests from more than one client at a time? Answer yes or no then explain your answer.

3. If a Web page contains a link to another page, must both pages be stored on the same server? Answer yes or no then explain your answer.

4. If a Web page contains a link to another page, may both pages be stored on the same server? Answer yes or no then explain your answer.

5. Do the terms client and server refer to hardware, software or both? Explain your answer.

6. At least two programs must be in your computer’s memory while you are surfing the Web – which programs?

7. What is in memory beside those programs while you are looking at a Web page on the screen?

Self-study questions

1. 2. 3. 4. 5.

Client Server

request

page

Without looking back, do you recall the steps in retrieving a Web page?