UDP port forwarder to multiple destinations?

[AvantLegion]

As seen in this thread: https://forums.gentoo.org/viewtopic.php?t=105694, I'm having an issue UDP traffic on a certain port - two devices are trying to get the same traffic from the same port. Everything works fine when only one device is on, but when both are, no data from that port gets through to anyone.

My router is a Gentoo box running iptables. I was told in the above thread that I probably needed a UDP port forwarder that could forward traffic to multiple desinations (makes sense). I'm Googling and seeing some stuff, but a helpful hint and recommendation would go far. Anyone experienced with this sort of thing?