This lecture goal is to develop a little Web Server.

This Web Server will serve HTTP requests, sent via a Web Browser using following

URLs:

http://www.ku.com/default.html

http://www.ku.com/index.asp

http://www.ku.com/win32.html

http://www.ku.com/courses/win32.html

Anatomy of a URL (Uniform Resource Locator):

http://www.ku.com/courses/win32.html

http:// protocol

www.ku.com Web Server

courses/win32.html location of file on server

Or http://www.ku.com:80/.../....

:80 is the specifies Port Number to use for connection

HTML stands for Hyper Text Mark-up Language.

This language contains text-formatting information e.g. font faces, font colors, font sizes,

HTML document on the Internet. HTML tags are embedded within normal text to make

it hypertext.

HTTP Client – a Web Browser examples are:

Microsoft Internet Explorer

Netscape Navigator

These web servers connect to your HTTP web server, requests a document, and displays

in its window

HTTP is a Stateless protocol.

MIME stands for Multi-purpose Internet Mail Extensions.

MIME contains encoding features, added to enable transfer of binary data, e.g. images

(GIF, JPEG etc.) via mail. Using MIME encoding HTTP can now transfer complex

binary data, e.g. images and video.

Short for Request for Comments, a series of notes about the Internet, started in 1969

(when the Internet was the ARPANET). An Internet Document can be submitted to the

IETF by anyone, but the IETF decides if the document becomes an RFC. Eventually, if it

gains enough interest, it may evolve into an Internet standard.

HTTP version 1.1 is derived from HTTP/1.1, Internet RFC 2616, Fielding, et al. Each

RFC is designated by an RFC number. Once published, an RFC never changes.

Modifications to an original RFC are assigned a new RFC number.

HTTP is a Text Transport Protocol

Transferring binary data over HTTP needs Data Encoding and Decoding because binary

characters are not permitted Similarly some characters are not permitted in a URL, e.g.

SPACE. Here, URL encoding is used

Including a Carriage Return / Line feed in a string

printf(“Line One\nThis is new line”);

Including a character in a string not found on our normal keyboards

printf(“The funny character \xB2”);

Represents the Home Directory of a Web Server

IIS (Internet Information Server) has c:\inetpub\wwwroot\ as its default Home Directory

Here, /courses/ either corresponds to a Physical Directory c:\inetpub\wwwroot\courses

OR Virtual Directoy

In a Web Server, we may specify that /courses/ will represent some other physical

directory on the Web Server like D:\MyWeb\. Then /courses/ will be a Virtual Directory.

In Windows2000 and IIS 5.0 (Internet Information Server), a folder’s “Web Sharing…”

is used to create a Virtual Directory for any folder.

GET /courses/win32.html HTTP/1.0

Request line is followed by 2 Carriage-Return /Line-feed sequences

Method Resource

Identifier

HTTP

Version

Crlf

Crlf

HTTP/1.1 200 OK }Status Line

Content-type: text/html

Crlf

Actual data follows the headers

File extensions are non-standard across different platforms and cannot be used to

determine the type of contents of any file.

Different common MIME types

image/gif GIF image

image/jpeg JPEG image

text/html HTML document

text/plain plain text

In an HTTP response, a Web Server tells the browser MIME type of data being sent

MIME type is used by the browser to handle the data appropriately i.e. show an image,

display HTML etc.

MIME: Multi-purpose Internet Mail Extensions MIME Encoding features were added

to enable transfer of binary data, e.g. images (GIF, JPEG etc.) via mail. Using MIME

encoding HTTP can now transfer complex binary data, e.g. images and video

MIME: Short for Multipurpose Internet Mail Extensions, a specification for formatting

non-ASCII messages so that they can be sent over the Internet.

HTTP version Status Code Description

Enables us to send and receive graphics, audio, and video files via the Internet mail

system.

There are many predefined MIME types, such as GIF graphics files and PostScript files.

It is also possible to define your own MIME types.

In addition to e-mail applications, Web browsers also support various MIME types. This

enables the browser to display or output files that are not in HTML format.

MIME was defined in 1992 by the Internet Engineering Task Force (IETF). A new

version, called S/MIME, supports encrypted messages.

404 Not Found

- requested document not found on this server

200 OK

- request secceeded, requested object later in this message

400 Bad Request

- request message not understood by server

302 Object Moved

- requested document has been moved to some other location

HTTP/1.1 302 Object Moved

Location: http://www.ku.com

crlf

Most browsers will send another HTTP request to the new location, i.e.

http://www.ku.com

This is called Browser Redirection

HTML text is received in one HTTP request from the Web Server

Browser reads all the HTML web page and paints its client area according to the HTML

tags specified. Browser generates one fresh HTTP request for each image specified in the

HTML file

Our server architecture will be based upon the following points

threads

Many WinSock function calls e.g. accept() are blocking calls

Server needs to serve up 5 clients simultaneously. Using other WinSock blocking calls,

need to perform termination tasks for asynchronously terminating communication

threads.

In this lecture, we studied some terms and their jobs. We studied HTTP (hyper

text transfer protocol) which is used to transfer text data across the net work. We also

studied HTML that is hyper text markup language which is simply a text script. Html is

loaded in web browser and web browser translates the text and executes instruction

written in form of text. For transferring media like image data and movie data, we

overviewed MIME.

1. Create a chat application. Using that application, you should be able to chat with

your friend on network.