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Web Clients

Web Clients. Chapter 2. Web Protocols and Practice. WEB CLIENTS. Topics. Web Protocols and Practice. WEB CLIENTS. Web Client Definition. Web Protocols and Practice. WEB CLIENTS. Web Client Definition. Web Protocols and Practice. WEB CLIENTS. Browser Functions.

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Web Clients

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  1. Web Clients Chapter 2 WebProtocolsandPractice

  2. WEB CLIENTS Topics WebProtocolsandPractice

  3. WEB CLIENTS Web Client Definition WebProtocolsandPractice

  4. WEB CLIENTS Web Client Definition WebProtocolsandPractice

  5. WEB CLIENTS Browser Functions WebProtocolsandPractice

  6. Browser DNS server WEB CLIENTS 1 DNS query URL Origin server 2 TCP Connection 3 HTTP Request 4 HTTP Response 5 Optional parallel connections Figure 2.1. Steps in a browser process WebProtocolsandPractice

  7. Figure 2.1 shows the various steps in the process involved in a Web request as processed by a typical browser. The selected URL is parsed to determine the Web server that must be contacted. A connection is set up with the server, and an HTTP request is sent with the URL to obtain the response.

  8. WEB CLIENTS Table 2.1. User action leading to request generation WebProtocolsandPractice

  9. WEB CLIENTS Canonical Web Transfer Example WebProtocolsandPractice

  10. WEB CLIENTS Table 2.2.Resources referred to in the canonical example and their content type WebProtocolsandPractice

  11. WEB CLIENTS Foo1.gif Foo2.gif Foo3.jpg Name: Address: :Credit Card :Book Title SUBMIT Mp.tv Book.cgi Figure 2.2. Container document foo.html WebProtocolsandPractice

  12. WEB CLIENTS Browser Caching WebProtocolsandPractice

  13. WEB CLIENTS Browser Caching WebProtocolsandPractice

  14. WEB CLIENTS Issuing Request By Browser WebProtocolsandPractice

  15. WEB CLIENTS Browser Configuration WebProtocolsandPractice

  16. WEB CLIENTS Browser Configuration WebProtocolsandPractice

  17. WEB CLIENTS Table 2.3.Helper applications launched based on file/content types WebProtocolsandPractice

  18. Browser WEB CLIENTS Foo.ra Origin server 1 HTTP request for foo.ra 2 (Location, protocol) 3 Audio protocol request Media server Audio client Figure 2.3. Listening to audio data WebProtocolsandPractice

  19. Figure 2.3: The user selects a resource http://www.bar.com/foo.ra, and the browser sends an HTTP request to the origin server www.bar.com for the resource foo.ca (step 1). The origin server sends back an HTTP response (step 2), but the content of the response is simply a pointer to the information. The response is meaningful only to an audio client rather than a Web browser. Typically, the response is a URL such as pnm://ra-ms.com/foo.ra, where pnm stands for "Progressive Network Media" and ra-ms is the media server on which the resource foo.ca resides. Because the browser has been configured to invoke the helper program based on the file type, it would invoke the real-audio client program, which would contact the media server ra-ms.com (step 3) and start downloading the audio content.

  20. WEB CLIENTS Browser Configuration WebProtocolsandPractice

  21. WEB CLIENTS Cookies WebProtocolsandPractice

  22. WEB CLIENTS Cookies WebProtocolsandPractice

  23. WEB CLIENTS Origin Server A Client Request Client Response Origin Server A Set-Cookie: XYZ Origin Server A Client Request Cookie: XYZ Figure 2.4. Client-server exchange of cookie information WebProtocolsandPractice

  24. Figure 2.4 shows a client sending a request to an origin server (step 1). The origin server in its response includes the header (Set-cookie) with the cookie value (XYZ) (step 2). In all future requests to the origin server A, the client includes the cookie (step3, sent with the request via the header cookie).

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