Hello,

Is there any possible way of getting the registered metadata values of a certain item/block while serverside? Kind  of like the  item.getSubItems  method, but that one is @SideOnly(Side.CLIENT). I basicly don't want to scroll through I don't even know how many values (-> 10000?) to check if that is a valid metadata value (I wouldn't even know how.), since that would be rather time consuming.

I don't think there is something like "registered metadata" - in your case damage values. It's on you, programmer, how you handle it. e.g. static final fields with hardcoded item dmg values for each item or enum. the method you're writing about is merely for a client to show stuff in creative gui, it does not limit you from using other damage values on item with same id.