-A PREROUTING -d 98.98.98.5/32 -p tcp -m tcp --dport 1050 -j DNAT --to-destination 192.168.1.50:3389
The above forwards port 1050 on IP 98.98.98.5 to 192.168.1.50 port 3389 (you can obviously edit things to meet your needs).
iptables, ip, dnat, prerouting, tcp, dport, destination, forwards, edit,