Communication between android phones

Question

Is it possible a communication between phones even without internet or Bluetooth in a specific area, lets say 20 meters through a app? Even if both persons dont know each others numbers?

Answer 1

If users knows only phone numder - try sms service :) For example. Send sms throught intent and catch sms throught Broadcast

Answer 2

You can use a wifi router without internet to do that. Just make one of the devices a server.

Answer 3

Yes that is possible for about 10 meters using wifi or direct-wifi. Let one phone function as wifi-hotspot and run your server app on that one. The other phone(s) connect to the wifi hotspot and then your client app can communicate with your server app because it will know the ip of the hotspot.