30http-2up - 30HTTP 14 Oct 2010 CSCC09F Programming on the...

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30HTTP 14 Oct 2010 CSCC09 Programming on the Web 1 30HTTP CSCC09 Programming on the Web 1 Protocols and HTTP, Web Browsers and Servers, Web Caching first some background on network- based applications … CSCC09F Programming on the Web 30HTTP CSCC09 Programming on the Web 2 Client-Server Paradigm Typical network app has two pieces: client and server Client: b initiates contact with server (“speaks first”) b typically requests service from server b for Web, client is implemented in browser; for e-mail, in mail user agent Server: b provides requested service to client b e.g., Web server sends requested Web page, mail server delivers e-mail application transport network data link physical application transport network data link physical request reply Internet
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30HTTP 14 Oct 2010 CSCC09 Programming on the Web 2 30HTTP CSCC09 Programming on the Web 3 Applications and application-layer protocols Application: communicating, distributed processes c running in network hosts in “user space” c exchange messages to implement application c e.g., email, file transfer, the Web, network news Application-layer protocols c one “piece” of an app c define messages exchanged by apps and actions taken c uses services provided by lower layer protocols application transport network data link physical application transport network data link physical application transport network data link physical Internet 30HTTP CSCC09 Programming on the Web 4 HTTP b HyperText Transfer Protocol b Part of Tim Berners-Lee’s innovation c Share results from physics experiments c Defined 1989-1991 b Standardized and much expanded by the IETF b Rides on top of “TCP” protocol c TCP provides: reliable, bi-directional, in-order byte stream (exists because Internet Protocol IP is unreliable) b Goal: transfer objects between systems c Do not confuse with other WWW concepts: B HTTP is not page layout language (that is HTML) B HTTP is not object naming scheme (that is URLs)
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30HTTP 14 Oct 2010 CSCC09 Programming on the Web 3 30HTTP CSCC09 Programming on the Web 5 The Web: HTTP protocol HTTP: HyperText Transfer Protocol b Web’s application-layer protocol b client/server model c client: (active) browser that requests, receives, “displays” Web objects c server: (passive) Web server sends objects in response to requests b http1.0: RFC 1945 b http1.1: RFC 2068 laptop running Mozilla Apache Web server H T P r e q u s t p o n smart phone running Micro-browser 30HTTP CSCC09 Programming on the Web 6 b Interaction between Web client (browser) and Web server occurs in two phases: c Request phase : Browser requests page from Web server c Response phase : Server sends back requested page or code b Protocol for each phase consists of: c Header (2 parts: request line or response status (single line), header fields (possibly multiple lines) c Body (request or response) HTTP 1.0 Request Response
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30HTTP 14 Oct 2010 CSCC09 Programming on the Web
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30http-2up - 30HTTP 14 Oct 2010 CSCC09F Programming on the...

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