Hi manishbhatnagar,
If you go into the listener, type:
lsnrctl
you will get to the prompt:
LSNRCTL>
type services
LSNRCTL> services
This will provide you with information on what databases this listener is listening for (if you have MTS, you will see listings for DISPATCHERS).
If you don't know about MTS then you probably don't use it.
Also, if you type help at the listener prompt it will give you some of the listener commands which can be usefull.
Best of luck,
Breen.