WebWeb ServersServers ProtocolsProtocols WebWeb ServerServer DefinitionDefinition :: AA computer,computer, includingincluding softwaresoftware package,package, thatthat providesprovides aa specificspecific kindkind ofof serviceservice toto clientclient softwaresoftware runningrunning onon otherother computers.computers. ...... AA WebWeb serverserver isis aa server-basedserver-based productproduct thatthat returnsreturns filesfiles toto clientsclients whenwhen requested.requested. TheseThese filesfiles areare typicallytypically returnedreturned inin thethe formform ofof WebWeb pagespages toto aa clientclient InternetInternet browser.browser. AA WebWeb ServerServer isis aa serverserver thatthat hostshosts websiteswebsites andand webweb applicationsapplications forfor thethe internetinternet oror aa companycompany intranet.intranet. MicrosoftMicrosoft InternetInternet InformationInformation ServerServer (IIS),(IIS), Apache,Apache, WebLogic,WebLogic, WebSphere,WebSphere, TomcatTomcat Sun,Sun, andand Lighttpd.Lighttpd. MostMost webweb serversservers areare builtbuilt forfor thethe JavaJava community,community, andand somesome areare openopen sourcesource likelike Apache.Apache. WhateverWhatever decisiondecision youyou makemake onon aa webweb serverserver willwill leadlead youyou downdown aa specificspecific developmentdevelopment roadroad (Microsoft(Microsoft vsvs Java).Java). HowHow WebWeb ServersServers WorkWork AA WebWeb serverserver handleshandles thethe HTTPHTTP protocol.protocol. WhenWhen thethe WebWeb serverserver receivesreceives anan HTTPHTTP request,request, itit respondsresponds withwith anan HTTPHTTP response,response, suchsuch asas sendingsending backback anan HTMLHTML page.page. ToTo processprocess aa request,request, aa WebWeb serverserver maymay respondrespond withwith aa staticstatic HTMLHTML pagepage oror image,image, sendsend aa redirect,redirect, oror delegatedelegate thethe dynamicdynamic responseresponse generationgeneration toto somesome otherother programprogram suchsuch asas CGICGI scripts,scripts, JSPsJSPs (JavaServer(JavaServer Pages),Pages), servlets,servlets, ASPsASPs (Active(Active ServerServer Pages),Pages), server-sideserver-side JavaScripts,JavaScripts, oror somesome otherother server-sideserver-side technology.technology. WhateverWhatever theirtheir purpose,purpose, suchsuch server-sideserver-side programsprograms generategenerate aa response,response, mostmost oftenoften inin HTML,HTML, forfor viewingviewing inin aa WebWeb browser.browser. WhenWhen aa requestrequest comescomes intointo thethe WebWeb server,server, thethe WebWeb serverserver simplysimply passespasses thethe requestrequest toto thethe programprogram bestbest ableable toto handlehandle it.it. TheThe WebWeb serverserver doesn'tdoesn't provideprovide anyany functionalityfunctionality beyondbeyond simplysimply providingproviding anan environmentenvironment inin whichwhich thethe server-sideserver-side programprogram cancan executeexecute andand passpass backback thethe generatedgenerated responses.responses. TheThe server-sideserver-side programprogram usuallyusually providesprovides forfor itselfitself suchsuch functionsfunctions asas transactiontransaction processing,processing, databasedatabase connectivity,connectivity, andand messaging.messaging. ThereThere areare somesome standardstandard capabilitiescapabilities thatthat allall webweb serversservers share.share. PricesPrices forfor webweb serversservers rangerange fromfrom freefree (Apache)(Apache) toto sortsort ofof freefree (you(you getget IISIIS automaticallyautomatically whenwhen youyou havehave aa WindowsWindows 200x200x server)server) toto expensiveexpensive (WebSphere).(WebSphere). MostMost webweb serversservers shareshare aa commoncommon setset ofof featuresfeatures andand functionalityfunctionality thatthat includeinclude contentcontent support,support, caching,caching, virtualvirtual hosting,hosting, authenticationauthentication andand performance.performance. WhichWhich serverserver youyou useuse dependsdepends onon aa numbernumber ofof thingsthings suchsuch as:as: AreAre youyou hostinghosting internallyinternally oror withwith aa serviceservice provider?provider? WhatWhat areare thethe developmentdevelopment skillsskills inin house?house? DoDo youyou havehave MicrosoftMicrosoft WindowsWindows ServersServers oror UnixUnix ServersServers inin house?house? WhatWhat isis youryour budget?budget? TheThe featuresfeatures andand functionalityfunctionality ofof webweb serversservers cancan bebe brokenbroken downdown intointo severalseveral areas:areas: ContentContent SupportSupport MostMost webweb serversservers serveserve bothboth staticstatic andand dynamicdynamic content.content. StaticStatic contentcontent isis htmlhtml andand images,images, stylesheets,stylesheets, etc.etc. DynamicDynamic contentcontent isis mademade upup ofof webweb pagespages thatthat needneed toto bebe processedprocessed byby somesome typetype ofof engine.engine. ExamplesExamples includeinclude webweb pagespages withwith serverserver sideside scriptingscripting suchsuch asas PHP,PHP, ASP.Net,ASP.Net, andand Javascript.Javascript. MostMost websiteswebsites andand applicationsapplications todaytoday areare builtbuilt usingusing dynamicdynamic content.content. TheThe abilityability toto cachecache versionsversions ofof aa webweb pagepage (whether(whether itsits htmlhtml oror aa processedprocessed dynamicdynamic page)page) inin aa locationlocation thatthat isis fasterfaster toto retrieveretrieve thanthan callingcalling andand processingprocessing thethe pagepage fromfrom thethe serverserver againagain isis anotheranother feature.feature. CachingCaching isis anan importantimportant capabilitycapability forfor websiteswebsites serverserver thousandsthousands oror millionsmillions ofof visitors.visitors. SiteSite HostingHosting GenerallyGenerally sitessites areare hostedhosted withwith theirtheir ownown IPIP address.address. CompaniesCompanies createcreate domaindomain namesnames forfor theirtheir websiteswebsites (i.e.(i.e. Suite101.com)Suite101.com) andand attachattach thatthat domaindomain namename toto thethe IPIP address.address. WhenWhen aa visitorvisitor typestypes aa domaindomain namename inin thethe browserbrowser thethe internetinternet translatestranslates itit toto itsits IPIP addressaddress andand sendssends thethe visitorvisitor toto thethe sitesite accordingly.accordingly. SomeSome webweb serversservers havehave thethe abilityability toto hosthost aa numbernumber ofof websiteswebsites onon aa singlesingle IPIP addressaddress usingusing aa processprocess calledcalled virtualvirtual hosting.hosting. ThisThis involvesinvolves associatingassociating sitessites toto distinctdistinct port/IPport/IP addressaddress combinationscombinations onon thethe server.server. ProcessProcess isolationisolation isis anan anotheranother featurefeature forfor aa webweb server.server. It’sIt’s importantimportant thatthat ifif somethingsomething happenshappens toto aa websitewebsite andand itit crashescrashes thatthat itit doesn’tdoesn’t bringbring downdown allall thethe otherother websiteswebsites thatthat residereside onon thethe server.server. ProcessProcess isolationisolation involvesinvolves settingsetting aa websitewebsite toto runrun inin itsits ownown processprocess onon thethe serverserver AuthenticationAuthentication WebWeb ServersServers mustmust supportsupport thethe abilityability toto authenticateauthenticate visitorsvisitors toto aa sitesite thatthat isis secure.secure. AnonymousAnonymous authenticationauthentication meansmeans thatthat everyoneeveryone hashas accessaccess andand therethere isis nono securitysecurity required.required. BasicBasic authenticationauthentication meansmeans thatthat aa useruser namename andand passwordpassword areare requiredrequired andand areare passedpassed toto thethe serverserver inin clearclear texttext (usually(usually byby enteringentering thethe usernameusername andand passwordpassword inin aa loginlogin screenscreen onon thethe website.website. WhileWhile thisthis isis secure,secure, it’sit’s openopen toto riskrisk becausebecause thethe securitysecurity credentialscredentials areare passedpassed inin clearclear text.text. NTLMNTLM isis aa MicrosoftMicrosoft securitysecurity protocolprotocol thatthat encryptsencrypts thethe credentialscredentials beforebefore beingbeing passed.passed. FinallyFinally allall webweb serversservers offeroffer SSL SSL (Secure(Secure SocketSocket Layer)Layer) whichwhich isis aa securesecure transporttransport layerlayer thatthat encryptsencrypts allall communicationscommunications betweenbetween thethe browserbrowser andand thethe webweb server.server. PortPort 443443 isis thethe mostmost commoncommon SSLSSL portport used.used. IfIf youyou useuse BasicBasic authenticationauthentication withwith SSLSSL youyou havehave aa muchmuch moremore securesecure authenticationauthentication process.process. PerformancePerformance AnotherAnother importantimportant aspectaspect forfor webweb serversservers isis performance.performance. HowHow wellwell dodo theythey performperform underunder load,load, howhow manymany requestsrequests (pages)(pages) areare serverserver perper minuteminute ((throughputthroughput),), howhow manymany usersusers cancan requestrequest contentcontent atat anyany givengiven timetime ((concurrencyconcurrency).). PerformancePerformance testingtesting ofof applicationsapplications isis anan importantimportant activityactivity whenwhen developingdeveloping aa websitewebsite andand thethe webweb