Discover mobile devices using wifi

I'm doing开发者_StackOverflow社区 some work for my theses in networking, and have stumbled into a little problem. One of the first steps in the work I must do consists on having a computer working as an AP (I am using hostapd for this) and with it, detect all the devices in the room which currently have wifi turned on (do not need to be associated with any AP).

I have found a thread that pretty much asks the same ( discover mobil devices using wifi ), and I understand the answers that were given, but they don't give any hint as to how this can be done. The post ends saying that the person was able to do this using Kismet, however I can only seem to use Kismet to discover clients already associated with an AP.

Can someone point me in the right direction here please? If not using Kismet, then maybe suggest a different tool that works with Ubuntu.

Ps. I will need to run a continuous scan of the "room" to find any new devices and then send this information to an event manager written in Java.

I guess you could have a WiFi card, in monitor mode, scanning every channel for beacons. On Linux, aircrack-ng is the tool suite you are looking for. airodump-ng is the tool that shows you a list of devices present around your location. It is designed to display first the hotspots with the potentials clients, but also shows all the devices that are connected to an AP or trying to probe to an AP.

However, you won't be able to scan devices having their WiFi connection turned down. I'm not sure about devices not associated to an AP, my guess is you will be able to detect them if they send beacons one way or another (for example, to detect WiFi hotspots).

If you need this in Java, you can write a wrapper to airodump-ng, or you can launch airodump-ng as a service outputing to a file and read this file from a Java app.

No concrete answer I'm afraid, but I hope these will help you figure a way to solve your problem.