skills: none concepts: web client (browser), web server, network connection, url, mobile client,...
Post on 15-Jan-2016
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TRANSCRIPT
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
Watch this video
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?