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What happens when you retrieve a Web page?

What happens when you retrieve a Web page?. Skills : none IT concepts : client, server, network service, network connection, URL, “Tiny” URL, Web client (browser), Web server, peer-to-peer. This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 License. .

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What happens when you retrieve a Web page?

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  1. What happens when you retrieve a Web page? Skills: none IT concepts: client, server, network service, network connection, URL, “Tiny” URL, Web client (browser), Web server, peer-to-peer This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 License.

  2. Where does this topic fit? • Internet concepts • Applications • Technology • Implications • Internet skills • Application development • Content creation

  3. Two computers connected to a network

  4. One running Internet client softwareThe other running Internet server software Server Client

  5. You enter a uniform resource locator (URL) into the address bar of the Web client program What happens next?

  6. Establish a temporary connection between the client and the server Server Client

  7. The client program sends a page request Request Server Client

  8. The server program sends the page document Server Client

  9. The client displays the page Client Server

  10. The page comes from server storage Client Server Request Web client program Web server program Document Memory Memory Requested page Requested page The Internet Display Storage

  11. The client-server conversation Client Server Open a connection Opens the connection OK GET <file location> Sends the docuemnt or an error message Display the response Close the connection OK

  12. What if the page is not on the server? If the server finds the page, it sends it back to the client; otherwise, it sends back an error message. The client is programmed to display whatever the server sends.

  13. Establish a temporary connection between the client and server (dotted line) Client sends the request to the server The server returns the requested page or an error message The client displays whatever the server returns Disconnect request page Server Client

  14. User clicks on a link to a second page 1. Get first page Server 1 2. Get second page Client Server 2

  15. Peer-to-peer applications • One computer can run both a client program and a server program For example • File sharing • Internet phone calls Internet service providers discourage home users from operating servers by charging more or limiting upstream speed.

  16. Mobile Web clients

  17. Web clients in things

  18. The parts of a URL http://bpastudio.csudh.edu/fac/lpress/shortbio.htm • This request is for a Web (http) server • The server program is running on a computer with the domain name bpastudio.csudh.edu • Look in a subdirectory called fac/lpress • If there is a file called shortbio.htm, send it back to the client to be displayed; if not, send an error message back to the client Domain name = the unique name of a computer on the Internet

  19. “Tiny” URLs – which do you prefer? http://www.csudh.edu/studentaffairs/financialaid/faq.shtml#apply_for_scholarships http://tinyurl.com/DHscholarship http://preview.tinyurl.com/DHscholarship (Made at http://www.tinyurl.com)

  20. Advertising business model

  21. A few URL questions • When opening the connection to the server, which part of the URL does the client use? • When retrieving a page from a server, which part of the URL does the server use? • What happens if you misspell the name of a file in a URL? • What happens if you misspell the domain name in a URL?

  22. Do the terms client and server refer to hardware or software? Don’t continue until you think you have the answer and can explain it.

  23. The big picture • A client is a computer running a client program • A server is a computer running a server program • A server offers a service to clients on the network • Clients use (geeks may say “consume”) those services

  24. A short video on the same topic World Wide Web in plain English http://www.commoncraft.com/world-wide-web

  25. request page Server Client Without looking back, can you recall the five steps we discussed in retrieving a Web page? 1. 2. 3. 4. 5.

  26. What happens when you retrieve a Web page? Skills: none IT concepts: client, server, network service, network connection, URL, “Tiny” URL, Web client (browser), Web server, peer-to-peer This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 License.

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