Chapter 3: Web Application Service and Cloud Computing (COMP 4442) Dr. Lei Yang [email protected] 3-1
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
3.1 What’s the HTTP? 3-3
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
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
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
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
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
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