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MIIS - 17. Introduction to the WWW & http * * http information from World Wide Web Programming with HTML & CGI by Ed Tittel, Mark Gaither, S. Hassinger, & Mike Erwin and Internet Agents Spiders, Wanderers, Brokers, and Bots by Fah-Chun Cheong. WWW. most graphical any point to any point
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MIIS - 17 Introduction to the WWW & http * * http information from World Wide Web Programming with HTML & CGI by Ed Tittel, Mark Gaither, S. Hassinger, & Mike Erwin and Internet Agents Spiders, Wanderers, Brokers, and Bots by Fah-Chun Cheong
WWW • most graphical • any point to any point • graphics mixed with text • History • CERN - European particle physics lab • Tim Berners-Lee • NCSA - National Center for Supercomputing Applications • Marc Andreessen
WWW uses • Museums • Newspapers • Magazines • Education • Government • Commerce • Individuals • Downside • lot of data • multiple connections required
Basic concepts • hyperlinking • Concept • anchor text (or graphic) • url • scheme://user:password@host:port/url-path • protocol • user, password, host system • path, filename • absolute versus relative urls • HTML • structure not format • tabs
http • TBL • generic, stateless object-oriented • application level • distributed • hypermedia • Object oriented • methods • extensions to basic http commands • associated with types of docs
Stateless • neither client or server stores info about state of the other side of the connection • given program can be client or server
http transaction • Connection • Request • Response • Close • More information • www.w3.org
Request • Full Request • method SP URI SP http-Version CRLF • *(General header | Request header | Entity header) CRLF • [Entity-Body] • methods • get, head, post, put, delete, link, unlink • headers • date, forwarded, message-id, mime-ver • accept, authorization, from, if-modified
Response • status line • http version SP status code SP explanation of response CRLF • *(General header | response head | Entity header) CRLF • [Entity-Body] • Classes of response codes • 1xx (Reserved for future) • 2xx (Successful) • 3xx (Further action required) • 4xx (Bad syntax in request) • 5xx (server failed on valid request)
Web browser • Presents document • Virtual terminal • Acts like required client • gopher, ftp, wais, telnet • Lynx • Mosaic • Emacs • Etc.
Web Server • Port 80 (by default) • Execute scripts (CGI) • NCSA • CERN
Future • HTML enhancements • New tags, inline graphics, better tables, better forms, toolbars (frames), validation • dynamic html, style sheets • Secure transactions • shttp, & SSL • authenticity • confidentiality • Uniform resource naming • URN • ISBN