Web Servers How do our requests for resources on the Internet get handled? Can they be located anywhere? Global?
Published byModified over 5 years ago
Presentation on theme: "Web Servers How do our requests for resources on the Internet get handled? Can they be located anywhere? Global?"— Presentation transcript:
1 Web ServersHow do our requests for resources on the Internet get handled?Can they be located anywhere? Global?
2 Web Servers Looking at …. Introduction to web servers HTTP request types3-tier system architectureAccessing a web server (local and remote)Web server examplesApacheTomcatIISPWS
3 What is a web server? Web server Specialized software that responds to client requests by providing resources (web pages, documents, etc..)Based on the client/server modelWhen users enter URL into Web browsers, they request specific documents from Web serverMaps URL to file on server and returns requested document to clientCommunicates with client using HTTPProtocol for transferring requests and files over the Internet
4 HTTP Request Types Also known as request methods Most popular are get and postRetrieve and send client form data to Web serverget requestSends form content as part of URLRetrieves appropriate resource from Web serverLimits query to 1024 characterspost requestUpdates contents of Web server (posting new messages to forum)Has no limit for length of queryNot part of URL and cannot be seen by user
5 HTTP Request Typesget and post requests are sent to a server-side form handlerClient browsers cache (save on disk) Web pagesAllows for quick reloadingCache responses to get requestDo not cache responses to post request
6 System ArchitectureA web server forms part of a multi-tier applicationDivide functionality into separate tiersLogical groupings of functionalityCan reside on same computer or on different computersWhat does a 3-tier architecture look like?let’s have a look
8 System Architecture Client tier Referred to as the top tier Application’s user interfaceUsers interact with application through user interfaceInteracts with middle tier to make requests and to retrieve data from information tierDisplays data to user
9 System Architecture Information tier Middle tier Referred to as data tier or bottom tierMaintains data for applicationStores data in relational database management systemMiddle tierImplements business logic and presentation logicControls interactions between application clients and application dataActs as intermediary between data in information tier and application clients
10 System Architecture Middle tier, cont. Controller logic Processes client requests from top tierRetrieves data from databasePresentation logicProcesses data from information tierPresents content to clientBusiness logicEnforces business rulesDictates how clients can access application data and how applications process dataEnsures data validity before updating database
11 Accessing Web Server Requesting documents Local Web server Must know machine name on which Web server residesThrough local Web servers or remote Web serversThrough domain name or Internet Protocol (IP) addressLocal Web serverResides on users’ machinesRequests documents in two waysMachine namelocalhostHost name that references local machine
12 Accessing Web Server Remote Web server Resides on different machines Accessing resources on remote web server requiresDomain nameRepresents group of hosts on InternetCombines with how name (www) and top-level domain to from fully qualified host nameFully qualified host nameProvides user friendly way to identify site on InternetIP addressUnique address for locating computers on InternetDNS (see notes)
13 Examples of Web Servers Apache (Apache group)Tomcat (Apache group)IIS (Microsoft Internet Information Services)PWS (Microsoft Personal Web Server)
14 Apache web server Apache Maintained by Apache Software FoundationCurrently most popular Web serverStableEfficientPortable(got it’s name from the original developers who called it ‘a patchy server’)
15 Apache web server Open source Freely distributed on the InternetHuge amount of end-user supportHas earned the reputation of being one of the most reliable web server availableUses server modules to add functionality to the core HTTP serveri.e. extra services that it can provide (e.g. security authentication)
16 Apache web server To launch Apache, successively select Start, Programs, Apache httpd Server, Control Apache Server and Start
17 Tomcat web server Tomcat Similar to Apache and also maintained by Apache Software FoundationFast becoming a popular Web serverBuilt in Servlet container (engine)Requires no add-ons to support Servlets
18 Tomcat web server To launch Tomcat, successively select Start, Programs, Apache Tomcat 4.x and Start Tomcat
19 Internet Information Services (IIS) web server Developed by MicrosoftIIS 5.0Enterprise-level Web serverIncluded with Windows 2000Allows computer to serve documentsUses an Internet Services Manager to administratesee diagram
20 Internet Information Services (IIS) web server Internet Services Manager dialog.
21 Personal Web Server (PWS) PWS developed by MicrosoftPWSScaled-down version of IISIntended for personal computers (PC)Ideal for educational institutions, small businesses and individualsDoes not require PC to be used exclusively as Web serverA Personal Web Manager is used to administrate it
22 Personal Web ServerPersonal Web Manager dialog.
23 References Check out http://www.apache.org http://www.microsoft.com Apache and Tomcat documentationApache and Tomcat are free to download and installIIS and PWS documentation
24 Summary We have looked at: Introduction to web servers HTTP request types3-tier system architectureAccessing a web server (local and remote)Web server examples