Hi Gayatri,
Please
UseCodeTags while posting code.
Does your server implementation extends UnicastRemoteObject? If yes, then you do not need to explicitly export it using UnicastRemoteObject.exportObject() methods. As soon as you initialize a class that extends UnicastRemoteObject, the object is exported by RMI.
If you try to export a class instance that extends UnicastRemoteObject, you will always get the exception that you have mentioned.