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Computer Networks with Internet Technology William Stallings

Computer Networks with Internet Technology William Stallings. Chapter 04 Modern Applications 4.1 Web Access - HTTP. Hypertext Transfer Protocol HTTP. Underlying protocol of the World Wide Web Not a protocol for transferring hypertext

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Computer Networks with Internet Technology William Stallings

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  1. Computer Networks with Internet TechnologyWilliam Stallings Chapter 04 Modern Applications 4.1 Web Access - HTTP

  2. Hypertext Transfer ProtocolHTTP • Underlying protocol of the World Wide Web • Not a protocol for transferring hypertext • For transmitting information with efficiency necessary for hypertext jumps • Can transfer plain text, hypertext, audio, images, and Internet accessible information

  3. HTTP Overview • Transaction oriented client/server protocol • Usually between Web browser (client) and Web server • Uses TCP connections • Stateless • Each transaction treated independently • Each new TCP connection for each transaction • Terminate connection when transaction complete

  4. Key Terms See Table 4.1 Page 116 • Cache • Client • Connection • Entity • Gateway • Message • Origin server • Proxy • Resource • Server • Tunnel • User agent

  5. HyperText Transfer Protocol (HTTP) • http://www.im.ncnu.edu.tw:80/~ycchen/http://www.im.ncnu.edu.tw/~ycchen/www/test.cgi?var1=123&var2=value2 • File Transfer Protocol (FTP) • ftp://ftp.ncnu.edu.tw/ • ftp://ftp.ncnu.edu.tw/JavaDownload/Docs/ftp://anonymous:guest@ftp.ncnu.edu.tw/ftp://ycchen@www.im.ncnu.edu.tw/ • Gopher Protocol (Gopher) • gopher://gopher.nsysu.edu.tw/11/traveler/train • Electronic Mail (Mailto) • mailto:username@ncnu.edu.tw • mailto:username@ncnu.edu.tw?subject=Hello! • Usenet News (News) • news:tw.bbs.rec.travelnews:* • Telnet to Remote Host (Telent) • telnet://bbs.ee.cycu.edu.tw/telnet://guest@bbs.ncnu.edu.tw/ • Host-Specific File Names (File) • file:///C|/My Documents/ URL Examples URL: Uniform Resource Locator

  6. Figure 4.1Examples of HTTP Operation

  7. Figure 4.2Intermediate HTTP Systems

  8. HTTP Messages • Requests • Client to server • Responses • Server to client • Request line • Response line • General header • Request header • Response header • Entity header • Entity body

  9. General Header Fields • Cache control • Connection • Data • Forwarded • Keep alive • MIME version • Pragma • Upgrade

  10. Request Methods • Request-Line = Method <SP> Request_URL <SP> HTTP-Version <CRLF> • Methods: • Options • Get • Head • Post • Put • Patch • Copy • Move • Delete • Link • Unlink • Trace • Wrapped • Extension-method

  11. Request Header Field • Accept • Accept charset • Accept encoding • Accept language • Authorization • From • Host • If modified since • Proxy authentication • Range • Referrer • Unless • User agent

  12. Response Messages • Status line followed by one or more general, response and entity headers, followed by optional entity body • Status-Line = HTTP-Version <SP> Status-Code <SP> Reason-Phrase <CRLF>

  13. Status Codes • Informational • Successful • Redirection • Client error • Server error

  14. Response Header Fields • Location • Proxy authentication • Public • Retry after • Server • WWW-Authenticate

  15. Allow Content encoding Content language Content length Content MD5 Content range Content type Content version Derived from Expires Last modified Link Title Transfer encoding URL header Extension header Entity Header Fields

  16. Entity Body • Arbitrary sequence of octets • HTTP transfers any type of data including: • text • binary data • audio • images • video • Interpretation of data determined by header fields • Content encoding, content type, transfer encoding

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