HTTP notes

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TCP/IP Protocol Suite 1

Upon completion you will be able to:

World Wide Web:World Wide Web:HTTPHTTP

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

Objectives


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1 ARCHITECTURE

The WWW is a distributed client-server service, in which a client using aThe WWW is a distributed client-server service, in which a client using abrowser can access a service using a server. The service provided isbrowser can access a service using a server. The service provided is

distributed over many locations called sites.distributed over many locations called sites.

The topics discussed in this section include:The topics discussed in this section include:

Client (Browser)Client (Browser)

ServerServer

Uniform Resource Locator (URL)Uniform Resource Locator (URL)

CookiesCookies


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Figure 1 Architecture of WWW


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Figure 2 Browser


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Figure 3 URL


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2 WEB DOCUMENTS

The documents in the WWW can be grouped into three broad categories:The documents in the WWW can be grouped into three broad categories:static, dynamic, and active. The category is based on the time thestatic, dynamic, and active. The category is based on the time the

contents of the document are determined.contents of the document are determined.


Static DocumentsStatic Documents

Dynamic DocumentsDynamic Documents

Active DocumentsActive Documents


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Figure 5 Boldface tags


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Figure 6 Effect of boldface tags


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Figure 7 Beginning and ending tags


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Figure 8 Dynamic document using CGI


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Figure 9 Dynamic document using server-site script


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Dynamic documents are sometimes

referred to as server-site dynamicdocuments.

Note:Note:


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Figure 10 Active document using Java applet


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Figure 11 Active document using client-site script


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Active documents are sometimes

referred to as client-site dynamicdocuments.

Note:Note:


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3 HTTP

The Hypertext Transfer Protocol (HTTP) is a protocol used mainly toThe Hypertext Transfer Protocol (HTTP) is a protocol used mainly toaccess data on the World Wide Web. HTTP functions like a combinationaccess data on the World Wide Web. HTTP functions like a combination

of FTP and SMTP.of FTP and SMTP.


HTTP TransactionHTTP Transaction

Persistent versus Nonpersistent ConnectionPersistent versus Nonpersistent Connection

Proxy ServerProxy Server


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HTTP uses the services of TCP on

well-known port 80.

Note:Note:


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Figure 12 HTTP transaction


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Figure 13 Request and response messages


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Figure 14 Request and status lines


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Table 1Table 1 MethodsMethods


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Table 2Table 2 Status codesStatus codes


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Table 2Table 2 Status codes (continued)Status codes (continued)


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Figure 15 Header format


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Table 3Table 3 General headersGeneral headers


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Table 4Table 4 Request headersRequest headers


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Table 5Table 5 Response headersResponse headers


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Table 6Table 6Entity headersEntity headers

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