As the title says, it is possible to duplicate all the items in your inventory
This is not achievable without a laggy or slow internet connection (aka you need one to dupe)
First, connect to the server on which you would like to duplicate items on
Second put the items in your inventory
Thirdly wait until you start to get connection lag. I use skype (blue circle that swirls) to tell me when my connection gets spotty
Forth quickly disconnect and reconnect. If you get it timed right you will see your character is still on the server as a sort of ghost. Kill the player and they will drop the items
And done! you will have the items in your inventory and the ones dropped by the ghost player
Ill upload pics later if it helps