Netbackup - OpsCenter port usage

Hi,

I have an instance of OpsCenter installed on a server, and would like to add a Netbackup Master appliance to it - can anyone confirm the firewall port requirements for doing this?

I've checked the KB article related to port usage, and it says 1556/TCP is used, but just says 'open 1556 between the appliance and opscenter' - it doesn't detail any direction..

What i'm unsure on, is if this is a bi-directional requirement, or just initated from OpsCenter to 1556 on the appliance (or the other way around..) 

Thanks!