There's either queue name (LPD protocol) or, there's port number 9100, 9101, 9102 to differentiate ports in HP JetDirect-Socket protocol. You have to go to the advanced Socket protocol to be able to enter the port number, because Apple has defaulted to 9100 in the easy setup.
Click ADD while holding down the option key, select Advanced from the bottom of the list that comes up, then select "AppSocket/HP JetDirect." name it. Fill in the URI:
socket://IP_address:9102
(9102 for third port)
Good luck.