But a share can consist of several different folders in different levels
on different drives etc, so the root part is still somewhat unclear.

not really. Conceptually, the root is defined on all systems as a node behind its own parent. Even if a share list looks like a directory, it is nothing less than a tree and the share list is just a node having all the directories you share mounted on it.

I never understood why the protocol had to be text-only, i mean, it Is a
_file_ (they are usually binary) sharing protocol, so a length specifyer
or similary wouldn't be difficult. I see some needs for being able to
communicate with the hub from a client with binary data to not be forced
to send it in a bandwidth eating way such as base32 or similar.

Yes, the binary vs text protocol troll is back :)

Eric