Yes you can.
I got my ip address, entered it on firefox, logged in, forwarded my ports (I followed the PortForward.com intructions so I think I did it right*), and then Blockland could not connect to my ports?
*I made the rule name "Application", a UDP, source ports any, destination ports range 28000-28030, WAN Connection Type "All Broadband Devices, Forward to Port: "Same as incoming port" When should this rule occur "Always" and entered this all. I have a Actiontec MI-424-WR router.