MIIS1 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

MIIS2 WWW u most graphical u any point to any point u graphics mixed with text u History –CERN - European particle physics lab –Tim Berners-Lee –NCSA - National Center for Supercomputing Applications –Marc Andreessen

MIIS3 WWW uses u Museums u Newspapers u Magazines u Education u Government u Commerce u Individuals u Downside –lot of data –multiple connections required

MIIS4 Basic concepts u hyperlinking –Concept F anchor text (or graphic) F url F –protocol –user, password, host system –path, filename –absolute versus relative urls u HTML –structure not format –tabs

MIIS5 http u TBL –generic, stateless object-oriented –application level u distributed u hypermedia u Object oriented –methods F extensions to basic http commands F associated with types of docs

MIIS6 Stateless u neither client or server stores info about state of the other side of the connection u given program can be client or server

MIIS7 http transaction u Connection u Request u Response u Close u More information –

MIIS8 Request u Full Request –method SP URI SP http-Version CRLF –*(General header | Request header | Entity header) CRLF –[Entity-Body] u methods –get, head, post, put, delete, link, unlink u headers –date, forwarded, message-id, mime-ver –accept, authorization, from, if-modified

MIIS9 Response u status line –http version SP status code SP explanation of response CRLF –*(General header | response head | Entity header) CRLF –[Entity-Body] u 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)

MIIS10 Web browser u Presents document u Virtual terminal u Acts like required client –gopher, ftp, wais, telnet u Lynx u Mosaic u Emacs u Etc.

MIIS11 Web Server u Port 80 (by default) u Execute scripts (CGI) u NCSA u CERN

MIIS12 Future u HTML enhancements –New tags, inline graphics, better tables, better forms, toolbars (frames), validation –dynamic html, style sheets u Secure transactions –shttp, & SSL –authenticity –confidentiality u Uniform resource naming –URN –ISBN