ITIS 1210 Introduction to Web-Based Information Systems Chapter 23 How Web Host Servers Work.

ITIS 1210ITIS 1210Introduction to Web-Based Introduction to Web-Based

Information SystemsInformation Systems

Chapter 23Chapter 23How Web Host Servers WorkHow Web Host Servers Work

IntroductionIntroduction

Websites need a place to live – a hostWebsites need a place to live – a host Websites are hosted on a serverWebsites are hosted on a server

StoredStored DistributedDistributed

ServerServer Manages communications protocolsManages communications protocols Houses the Web pages themselvesHouses the Web pages themselves Supporting softwareSupporting software

IntroductionIntroduction

Server softwareServer software Delivers the pages requested by clientsDelivers the pages requested by clients Acts on other requests from serversActs on other requests from servers Handles the HTTP requestsHandles the HTTP requests Communicates with the host’s OSCommunicates with the host’s OS

Which handles the TCP/IP functionsWhich handles the TCP/IP functions

How Web Host Servers WorkHow Web Host Servers Work

Different types of server software handle Different types of server software handle different kinds of requests from clientsdifferent kinds of requests from clients Database serversDatabase servers FTP requestsFTP requests Network serversNetwork servers Mail serversMail servers

WebWeb servers are HTTP servers servers are HTTP servers Sends HTML documents using HTTPSends HTML documents using HTTP


Most of the time, the client requests an Most of the time, the client requests an HTML pageHTML page Server receives requestServer receives request Locates the .html fileLocates the .html file Sends it back to the requesting clientSends it back to the requesting client

Can do more howeverCan do more however Passes requests to run CGI scripts to CGI Passes requests to run CGI scripts to CGI

applicationsapplications


These scripts run external mini-programs These scripts run external mini-programs Database lookupDatabase lookup Process and interactive formProcess and interactive form

Server sends script to CGIServer sends script to CGI In a standardized formatIn a standardized format

CGI communicates with external programCGI communicates with external program Receives results back from external programReceives results back from external program Formats & returns resultsFormats & returns results


Basic problem with IP addresses:Basic problem with IP addresses: They are limited in scope because of their 0-They are limited in scope because of their 0-

255 format255 format

IP addresses allow you to contact a IP addresses allow you to contact a specific computerspecific computer

But how does that computer know which But how does that computer know which program you are using?program you are using?


The answer is port numbersThe answer is port numbers Value from 0 to 65535Value from 0 to 65535

Think of it as the extension of a telephone Think of it as the extension of a telephone numbernumber

A complete data transfer always includes A complete data transfer always includes a port number:a port number:


213.153.38.220:80

ITIS 1210 Introduction to Web-Based Information Systems Chapter 23 How Web Host Servers Work.

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