When i just have 2 clients syncing with each other and one of them is not permanently available to sync, this isnt going to work very good right ? So id need s

When i just have 2 clients syncing with each other and one of them is not permanently available to sync, this isnt going to work very good right ? So id need some central always-on server to sync my stuff to, to habe it all synced and secure all the time.