title: android - array list update in two users online
body: <p>i need to provide me the way to do this:</p>
  
  <p>for example i have application that the content recyclerview there is button to add items into recyclerview ,
  note : this above part i knew how do it:
  but :</p>
  
  <p>when i add item in recyclerview immediately it will add in my friend online 
   as well when will be delete it will delete from my freind in real time .</p>
  
  <p>also it will send in specific user in app so app content users in online host </p>
  
  <p>but the problem is how to send in realtime to specific user and do it?</p>