How to list clients that have used your wifi hotspot on a Nexus 5
If your phone is rooted, you can open the file located at /data/misc/dhcp/dnsmasq.leases with an editor. There you can see information about connected devices.

Source: https://stackoverflow.com/questions/9996351/wi-fi-tethering-how-to-get-list-of-connected-clients

(This I maybe duplicate of the link provided)