I want to make application which gives me the list of all the devices that are connected to my current network connection.
For eg. When i press on search button in bluet
If you mean you want to see all the devices connected to your current WiFi connection (and you are not trying to do Ad Hoc networking), then you are essentially wanting to run a network scanner.
There are a bunch of these around. This one has the source available on github
http://rorist.github.com/android-network-discovery/
This is possible now to get the network devices using NSD Android new feature and for this required minimum version 16 level Jellybean
Here is the link for NSD
http://developer.android.com/training/connect-devices-wirelessly/nsd.html