IP address changed

[NEO000]

I create a free wireless network with my wifi router app. It works well and you can see the IP address of connected device directly. But sometimes the addresses are changed. Is there any way to see which is which even they change the device's IP address?

[GuiltySpark]

Open up a cmd prompt as Admin and type nslookup <and whichever the IP for a given device is here> (minus the <> brackets.
It may give you a name for that device.