Logged on Users in Portal

Hi,

I want to list all the users who have logged into the portal using a webdynpro for Java application.

Please guide me with this.

I will deploy the Java application on the Portal and when it runs it needs to pick out all the users with active sessions in this Enterprise Portal and display it.

should be like SM04 in R/3 system.

Points coming your way.

Regards,

Abhishek