title: need mechanism to detect client connections to portable hotspot
body: <p>My android phone is acting as a portable hotspot to which several clients may connect.
  Please suggest a mechanism to detect/listen/receive notification whenever a client connects or disconnects to/from the hotspot.</p>
  
  <p>All clients connecting to the hotspot are serial device servers. Since my tablet/phone(hotspot) is on the move, clients keep disconnecting and reconnecting to it depending on the range, and I need to track their connection status.</p>
  
  <p>Currentl approach: I am executing a thread that sends udp discovery requests from the android phone, receives responses from clients and store their details in a Map.<br>
  What I am looking for is a more efficeint way to detect disconnections and reconnections as and when they happen.</p>