udp port forward

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Option 1: user-application based udp port forwarding

Ivan Tikhonov wrote a simple udp_redirect.c program to do just this. I like it.

The link: http://brokestream.com/udp_redirect.html

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Option 2 is to use iptables.

You will need to set the middle computer (Linux) to
1. NAT
2. port forward to the local computer

iptables -t nat -A POSTROUTING -j MASQUERADE -o eth0
iptables -t nat -A PREROUTING -p udp -i eth0 --dport 161  -j DNAT --to 192.168.1.10

Then set the local computer's default gateway to the middle computer:

route add default gw 192.168.1.100

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If you are looking for TCP port forwarding, I use and recommend the open source program rinetd. It works on both Windows and Linux, and supports multiple TCP connections, and is very stable. The link: http://www.boutell.com/rinetd/