Tracking any kind of user activity is known as Session tracking,

        Session comes in two favor 

                    1. Statefull session

                    2. Stateless Session

It creates a channel between client and server, session will be closed if any one of the end get disturbed. And they need to re-authenticate again to continue their process.

Example: SSH, FTP, Telnet etc

Once the user is authenticated it maintains a token to do the further process, so there is no need to maintain any channel between client and server, the client needs to re-authenticate if the token is lost or expired.

Example: http protocol, all web based application.

The token can be maintained on either client or server side

Consider a web based application, token can be maintained on client using 3 ways

            1. Cookie

            2. URL-rewriting

            3. HiddenForm

Server side Servlets programming.

            1. HttpSession can be used to maintain token on server side.

Related Example

    Login logout example using Cookie

    Login logout example using HttpSession