Nanoflow run on client side which is on browser , thats why they can run offline also and in any offline application
if you need data from server you can pull or once you go online . So client side can give a call to server because server is known .
Now assume the reverse situation if you try to give a call to client side from server how you know where you pass the call client will be unknow . Not at all possible . That's
websockets are used when you want to push real time data