Thanks in advance for any help.
That depends on your server. You could use push notifications, sockets, websockets or long polling. If I was going to make something from scratch I would probably use a combination. Push notification when in the background and then do a http fetch (to sync latest) when going into foreground while waiting for websockets to reconnect.
Is there any example you could point me to for any of this – even the roughest skeleton would be great.