Directing TCP traffic from one OS X server to another?

Thanks in advance for any help you could give me.

I have a Jabber server set up on our internal server for internal communications, on TCP port 5223.

A second server on our network is a webserver, with an ADSL connection on one of its ethernet ports with a 192.168.*.* network, and the other port is connected to the same network as our server with Jabber on it. IP being 10.90.*.*

What i'd like to do is have a web based jabber client on our webserver, and have it be able to connect to our Jabber server so our users can connect to our internal jabber server from the outside of the company.

So the question i'd like to ask is, how (In Mac OS X Leopard Server) can i get incoming TCP traffic on one ethernet port to divert through to another server? Neither servers have a firewall enabled at the moment.

Hope that makes sense. Thanks again.