set other port in another pc, and forward the port to it's ip
for instance
you have pc A and B
A uses 123,456,789, IP:192.168.1.1
B uses 924,925,926, IP:192.168.1.2
forward 123,456,789 to 192.168.1.1
forward 924,925,926 to 192.168.1.2
and create two entries, by using diff ports with the same wan ip