Web Server

•It is a computing server that enables HTTP access to a web site.

•A web server runs many additional  services behind the scene, e.g., a database, a server application framework, authentication, etc.

•Web server refer to either the hardware (the computer) or the software (the computer application) that helps to deliver web content that can be accessed through the Internet.
The term web server or webserver can mean one of two things:

–A computer program that accepts HTTP requests and return HTTP responses with optional data content.

–A computer that runs a computer program as described above. 

Web Server Components

A web server typically include the following major components:

•networking support : sending responses and receiving requests over the network;

•address/domain resolution : analyzing the correct IP address for the requested (virtual) domain, authenticating if necessary;

•request processing : serving static or dynamic content as appropriate;

response generation : building the response and passing it to the networking component.

Web Server Workflow

A web server has the following workflow steps:

1.receive a HTTP request;

2.translate the resource “path” based on the requesting URL;

3.check access based on the requested information;

4.validate the user id and authenticate the user if necessary;

5.determine the MIME (Multi-purpose Internet Mail Extensions) type of the requested resource;

6.generate the dynamic response if needed, i.e., running local scripts;

7.send response back

8.log the request.

URI(Uniform Resource Identifier )

•It contains four distinct parts: the protocol 

type, the machine name, the directory path and the file name.

•URI stands for Uniform Resource Identifier. URI is a text which is used to identify any resource or name in Internet.

• URI has two specialization in form of URL (Uniform Resource Locator) and URN (Uniform Resource Name) to identify resource and name.

URI(Uniform Resource Identifier )

URL (Uniform Resource Locator)

•Location dependent and is a subset of URI or Uniform Resource Identifier.

•Includes location as well as protocol to retrieve the resource e.g. in http://abc.com/foldarname/filename.html, HTTP is a protocol which can be used to retrieve resource filename.htm available in location http://abc.com directory.

•There are several kinds of URLs: file URLs, FTP URLs, and HTTP URLs.

•It's not necessary that URL always include http as protocol, it can use any protocol e.g. ftp://, https://

URN (Uniform Resource Name)

•URN is also subset of URI. One of the best example of URN is ISBN number which is used to uniquely identify a book.

• URN is completely different than URL as it doesn't include any protocol