Lecture 3 - Webapps - v1.1 - Chapter 3 Web Application Service and Cloud Computing(COMP 4442 Dr Lei Yang [email protected] 3-1 Chapter 3 roadmap 3.1

Lecture 3 - Webapps - v1.1 - Chapter 3 Web Application...

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Chapter 3: Web Application Service and Cloud Computing (COMP 4442) Dr. Lei Yang [email protected] 3-1
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Chapter 3: roadmap 3.1 What’s the HTTP? 3.2 What’s a HTTP Server Sta±c web server Dynamic web server 3.3 Java Web Applica±on 3.4 Summary 3-2
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3.1 What’s the HTTP? 3-3
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Internet protocol stack applicaton: supportng neTwork applicatons F±P, SM±P, HTTP TransporT: process-process daTa Transfer ±CP, UDP neTwork: routng of daTagrams from source To destnaton IP, routng proTocols link: daTa Transfer beTween neighboring neTwork elemenTs ETherneT, 802.111 (WiFi), PPP physical: biTs “on The wire” application transport network link physical 3-4
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HyperText Transfer Protocol (HTTP) An applicaton-layer proTocol for disTribuTed, collaboratve, hypermedia informaton sysTems. Providing fundamenTal means of exchanging informaton and requestng services on web On Top of The ±CP (±ransmission ConTrol ProTocol) Capabilites ( H±±P 1.0 ) Allow messages in The MIME (Multpurpose InTerneT Mail ExTensions) formaT ConTain meTa-informaton abouT: DaTa Transferred ModiFers on The requesT/response semantcs ( H±±P 1.1 ) SupporT for hierarchical proxies, caching, persisTenT connectons, virTual hosTs DeTermine applicatons’ True capabilites ±exT-based ProTocol 3-5
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HTTP overview Web’s application layer protocol client/server model client : browser that requests, receives, (using HTTP protocol) and “displays” Web objects server: Web server sends (using HTTP protocol) objects in response to requests PC running Firefox browser server running Apache Web server iphone running Safari browser H T P r e q u s t p o n 3-6
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HTTP overview (contnued ) uses TCP: client initiates TCP connection (creates socket) to server, port 80 server accepts TCP connection from client HTTP messages (application-layer protocol messages) exchanged between browser (HTTP client) and Web server (HTTP server) TCP connection closed HTTP is “stateless” server maintains no information about past client requests protocols that maintain “state” are complex! past history (state) must be maintained if server/client crashes, their views of “state” may be inconsistent, must be reconciled aside 3-7
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Non-persistent HTTP suppose user enters URL: 1a . HTTP client initiates TCP connection to HTTP server (process) at on port 80 2 . HTTP client sends HTTP request message (containing URL) into TCP connection socket. Message indicates that client wants object someDepartment/home.i ndex 1b . HTTP server at host waiting for TCP connection at port 80. “accepts” connection, notifying client 3 . HTTP server receives request message, forms response message containing requested object, and sends message into its socket time (contains text, references to 10 jpeg images) 3-8
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Non-persistent HTTP (cont.) 5 . HTTP client receives response message containing html fle, displays html.
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  • Summer '19
  • World Wide Web, Web server, Web browser, Hypertext Transfer Protocol, HTTP

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