Transcript Chapter 23 - Personal Web Pages

ITIS 1210
Introduction to Web-Based
Information Systems
Chapter 23
How Web Host Servers Work
Introduction
 Websites need a place to live – a host
 Websites are hosted on a server
 Stored
 Distributed
 Server
 Manages communications protocols
 Houses the Web pages themselves
 Supporting software
Introduction
 Server software
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Delivers the pages requested by clients
Acts on other requests from servers
Handles the HTTP requests
Communicates with the host’s OS
 Which handles the TCP/IP functions
How Web Host Servers Work
 Different types of server software handle
different kinds of requests from clients
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Database servers
FTP requests
Network servers
Mail servers
 Web servers are HTTP servers
 Sends HTML documents using HTTP
How Web Host Servers Work
 Most of the time, the client requests an
HTML page
 Server receives request
 Locates the .html file
 Sends it back to the requesting client
 Can do more however
 Passes requests to run CGI scripts to CGI
applications
How Web Host Servers Work
 These scripts run external mini-programs
 Database lookup
 Process and interactive form
 Server sends script to CGI
 In a standardized format
 CGI communicates with external program
 Receives results back from external program
 Formats & returns results
How Web Host Servers Work
 Basic problem with IP addresses:
 They are limited in scope because of their 0255 format
 IP addresses allow you to contact a
specific computer
 But how does that computer know which
program you are using?
How Web Host Servers Work
 The answer is port numbers
 Value from 0 to 65535
 Think of it as the extension of a telephone
number
 A complete data transfer always includes
a port number:
How Web Host Servers Work
213.153.38.220:80