Well because your not forwarding it. A forward is when certian traffic is assigned to a certian port on your WAN, its assigned to a certian IP with the same port. What you need to do is set up a trigger that when port 44948 is triggered on your WAN, that traffic is assigned to a different port on your LAN. The conflict is your trying to direct two ports on the WAN to the same port on your LAN. A trigger will only activivate on request, while a forwarding acts all the time.
First, you might want to look at your ISP's TOS, and see if this is allowed. Many ISP's block some of these ports to stop you from hosting a server from your house, and since that is what your looking to do (albeit a small one) they may frown apon it.
With that said, you will need to use the Virtual Server Function. More info can be found
here Good luck