Hi Umesh,
 
If you are using the Login/Logout actions of the CUAE extension mobility, then you can use the result code as the notification for the CUAE server.
 
You can look at this page : http://developer.cisco.com/static/cuae/2.5/2.5.1SR1/Designer/index.html
 
The other approach could be using the Presence.
 
Regards,
Rakesh.

In addition to what David mentioned, if you are using 2.5.1 SR2, your application will get Address events (AddressInService) as well. This will give you the lineDNs on the devices.
 
The following new triggering events were added to the JTAPI 3rd-party API to provide address change notifications:
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¿JTapiAddressAddedToTerminal
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¿JTapiAddressRemovedFromTerminal
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¿JTapiAddressInService
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¿JTapiAddressOutService
 
Please refer to the 2.5.1 SR2 release notes for more information.
 
Thanks,
Rajesh