For example, if on your Android phone to raise the Wi-Fi hotspot (say, the telephone itself to anything connected, so Internet access will not, but it's kind of unimportant), and a nearby laptop to connect to this point, and then the phone shut off point, then on the laptop a few seconds it will disappear.
It turns out, the laptop somehow monitors the accessibility point as the server (monitors on the principle of keep-alive in TCP, or something like that), regardless of TCP/UDP and above.
So - how is the Protocol that sent these messages?
I say at once - the question is purely for the overall development. Track using is open in your client / server app I'm not going to know what that would be wrong.