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Chap 22 www http


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Chap 22 www http

  1. 1. CChhaapptteerr 2222 WWoorrlldd WWiiddee WWeebb:: HHTTTTPP Objectives Upon completion you will be able to: • Understand the components of a browser and a server • Understand the function of the URL and cookies • Understand how HTML is related to static documents • Understand how CGI is related to dynamic documents • Understand how Java is related to active documents • Know how HTTP accesses data on the WWW TCP/IP Protocol Suite 1
  2. 2. 22.1 ARCHITECTURE The WWW is a distributed client-server service, in which aa cclliieenntt uussiinngg aa bbrroowwsseerr ccaann aacccceessss aa sseerrvviiccee uussiinngg aa sseerrvveerr.. TThhee sseerrvviiccee pprroovviiddeedd iiss ddiissttrriibbuutteedd oovveerr mmaannyy llooccaattiioonnss ccaalllleedd ssiitteess.. TThhee ttooppiiccss ddiissccuusssseedd iinn tthhiiss sseeccttiioonn iinncclluuddee:: CClliieenntt ((BBrroowwsseerr)) SSeerrvveerr UUnniiffoorrmm RReessoouurrccee LLooccaattoorr ((UURRLL)) CCooookkiieess TCP/IP Protocol Suite 2
  3. 3. Figure 22.1 Architecture of WWW TCP/IP Protocol Suite 3
  4. 4. Figure 22.2 Browser TCP/IP Protocol Suite 4
  5. 5. Figure 22.3 URL TCP/IP Protocol Suite 5
  6. 6. 22.2 WEB DOCUMENTS The documents in the WWW can be grouped into tthhrreeee bbrrooaadd ccaatteeggoorriieess:: ssttaattiicc,, ddyynnaammiicc,, aanndd aaccttiivvee.. TThhee ccaatteeggoorryy iiss bbaasseedd oonn tthhee ttiimmee tthhee ccoonntteennttss ooff tthhee ddooccuummeenntt aarree ddeetteerrmmiinneedd.. TThhee ttooppiiccss ddiissccuusssseedd iinn tthhiiss sseeccttiioonn iinncclluuddee:: SSttaattiicc DDooccuummeennttss DDyynnaammiicc DDooccuummeennttss AAccttiivvee DDooccuummeennttss TCP/IP Protocol Suite 6
  7. 7. Figure 22.4 Static document TCP/IP Protocol Suite 7
  8. 8. Figure 22.5 Boldface tags TCP/IP Protocol Suite 8
  9. 9. Figure 22.6 Effect of boldface tags TCP/IP Protocol Suite 9
  10. 10. Figure 22.7 Beginning and ending tags TCP/IP Protocol Suite 10
  11. 11. Figure 22.8 Dynamic document using CGI TCP/IP Protocol Suite 11
  12. 12. Figure 22.9 Dynamic document using server-site script TCP/IP Protocol Suite 12
  13. 13. NNoottee:: Dynamic documents are sometimes referred to as server-site dynamic documents. TCP/IP Protocol Suite 13
  14. 14. Figure 22.10 Active document using Java applet TCP/IP Protocol Suite 14
  15. 15. Figure 22.11 Active document using client-site script TCP/IP Protocol Suite 15
  16. 16. NNoottee:: Active documents are sometimes referred to as client-site dynamic documents. TCP/IP Protocol Suite 16
  17. 17. 22.3 HTTP The Hypertext Transfer Protocol (HTTP) is a protocol uusseedd mmaaiinnllyy ttoo aacccceessss ddaattaa oonn tthhee WWoorrlldd WWiiddee WWeebb.. HHTTTTPP ffuunnccttiioonnss lliikkee aa ccoommbbiinnaattiioonn ooff FFTTPP aanndd SSMMTTPP.. TThhee ttooppiiccss ddiissccuusssseedd iinn tthhiiss sseeccttiioonn iinncclluuddee:: HHTTTTPP TTrraannssaaccttiioonn PPeerrssiisstteenntt vveerrssuuss NNoonnppeerrssiisstteenntt CCoonnnneeccttiioonn PPrrooxxyy SSeerrvveerr TCP/IP Protocol Suite 17
  18. 18. NNoottee:: HTTP uses the services of TCP on well-known port 80. TCP/IP Protocol Suite 18
  19. 19. Figure 22.12 HTTP transaction TCP/IP Protocol Suite 19
  20. 20. Figure 22.13 Request and response messages TCP/IP Protocol Suite 20
  21. 21. Figure 22.14 Request and status lines TCP/IP Protocol Suite 21
  22. 22. TTaabbllee 2222..11 MMeetthhooddss TCP/IP Protocol Suite 22
  23. 23. TTaabbllee 2222..22 SSttaattuuss ccooddeess TCP/IP Protocol Suite 23
  24. 24. TTaabbllee 2222..22 SSttaattuuss ccooddeess ((ccoonnttiinnuueedd)) TCP/IP Protocol Suite 24
  25. 25. Figure 22.15 Header format TCP/IP Protocol Suite 25
  26. 26. TTaabbllee 2222..33 GGeenneerraall hheeaaddeerrss TCP/IP Protocol Suite 26
  27. 27. TTaabbllee 2222..44 RReeqquueesstt hheeaaddeerrss TCP/IP Protocol Suite 27
  28. 28. TTaabbllee 2222..55 RReessppoonnssee hheeaaddeerrss TCP/IP Protocol Suite 28
  29. 29. TTaabbllee 2222..66 EEnnttiittyy hheeaaddeerrss TCP/IP Protocol Suite 29
  30. 30. ExamplE 1 This example retrieves a document. We use the GET method to retrieve an image with the path /usr/bin/image1. The request line shows the method (GET), the URL, and the HTTP version (1.1). The header has two lines that show that the client can accept images in the GIF or JPEG format. The request does not have a body. The response message contains the status line and four lines of header. The header lines define the date, server, MIME version, and length of the document. The body of the document follows the header (see Figure 22.16). See Next Slide TCP/IP Protocol Suite 30
  31. 31. Figure 22.16 Example 1 TCP/IP Protocol Suite 31
  32. 32. ExamplE 2 In this example, the client wants to send data to the server. We use the POST method. The request line shows the method (POST), URL, and HTTP version (1.1). There are four lines of headers. The request body contains the input information. The response message contains the status line and four lines of headers. The created document, which is a CGI document, is included as the body (see Figure 22.17). See Next Slide TCP/IP Protocol Suite 32
  33. 33. Figure 22.17 Example 2 TCP/IP Protocol Suite 33
  34. 34. ExamplE 3 HTTP uses ASCII characters. A client can directly connect to a server using TELNET, which logs into port 80. The next three lines shows that the connection is successful. We then type three lines. The first shows the request line (GET method), the second is the header (defining the host), the third is a blank terminating the request. The server response is seven lines starting with the status line. The blank line at the end terminates the server response. The file of 14230 lines is received after the blank line (not shown here). The last line is the output by the client. See Next Slide TCP/IP Protocol Suite 34
  35. 35. ExamplE 3 $ telnet www.mhhe.com 80 Trying Connected to www.mhhe.com ( Escape character is '^]'. GET /engcs/compsci/forouzan HTTP/1.1 From: forouzanbehrouz@fhda.edu HTTP/1.1 200 OK Date: Thu, 28 Oct 2004 16:27:46 GMT Server: Apache/1.3.9 (Unix) ApacheJServ/1.1.2 PHP/4.1.2 PHP/3.0.18 MIME-version:1.0 Content-Type: text/html Last-modified: Friday, 15-Oct-04 02:11:31 GMT Content-length: 14230 Connection closed by foreign host. TCP/IP Protocol Suite 35
  36. 36. NNoottee:: HTTP version 1.1 specifies a persistent connection by default. TCP/IP Protocol Suite 36