2 PC with the same name

Can these names have SPACE " " in them or do they need to adhere to the DNS name format?

Hi, just added 2 PCs, they technically have the same name… will this create an issue (they are both outside the LAN, the first one works, the second says its connected by the server never says its online, is this due to the machine name being the same as another PC?

Turns out you cant have 2 systems with the same name, the second one might connect to the server, but the server never sends any data too it…

We removed that second system from the server, created a new system with a new name, then on the client used that new name, added the new created ID, restarted the UrBackup service (Windows) and now it talks with the server ok (and backs stuff up).