Web Servers: The Engines that Drive the World Wide Web

Dr. William FarmerReza Sherafat

McMaster UniversityMay 3, 2006

Outline

Computer Networks

The client-server model

Creating and installing a web page

How a web server works

Computer Networks

A network is a group of computers connected together

The Internet is the global computer network

Different services are provided by servers across the Internet and clients access those services

Network Addresses To be identified on the network, computers have unique

addresses associated with them

The addresses are managed by a protocol called Internet Protocol (IP)

192.168.17.3 is an IP address

IP addresses are hard to remember, so to be more readable Hostnames are used

Each host name is associated with one IP address

www.mcmaster.ca is a hostname which is equivalent to 130.113.64.64

Fundamentals

Computer applications

Process: a running program in a computer

To be able to access the outside world on the network, processes communicate through ports.

Port: entry points to a computer system (denoted by a port #).

Client – Server Model

Process

Port

ServerClient 2

Client 1

Connection

Client – Server Model

A server process provides services.

A server process at a server listens to a port, and is ready to receive client requests.

A client process at a host, communicates to the server process by connecting to the port # that the service is listening to.

The client has to know the server address, the server port # and the protocol to communicate to the server process.

Protocols

Daytime service [RFC867]:Client: Hello, <client address> here. May I have a timestamp

please.Server: Here it is: (time stamp follows)

World Wide Web session (HTTP):Client: Hello, <client address> here. Server: Okay. I am a web server and speaks protocol HTTP1.0.Client: Great, please get me the web page index.html at the root

of your document tree.Server: Okay, here’s what’s in the page: (contents follows).

HTTP Protocol

Server

GETPage1.html

Page1.html

HTTP Protocol

Server

GETImage.jpg

The browser at the client parses the HTML document and determines that some pictures should also be loaded.

- The browser request the image files the same way.

Client – Server Model

The request/response sequence continues …

clie n t s e rve r

re qu e s t 1

re qu e s t 2

re qu e s t n

re s pon s e 1

re s pon s e 2

re s pon s e n

Write/upload and access your own online content Open a browser and retrieve the template at

http://wiglaf.cas.mcmaster.ca/workshop/template/

You need to edit the template and fill it out with your own information. You may use any text editor (e.g. notepad)

You can easily change the Page title Content Pictures: You can use the images that you find from the web.

Save your changes to the template, and rename it.

Upload you new file using the upload page at http://wiglaf.cas.mcmaster.ca/workshop/upload/

Use the link to access your page.

How a web server works?