Packets forwarding

Hello, I have the following problem:
I have a device which transmits packets on a specific port to some IP
address. I would like it to transmit to some dynamic domain but can't
- I can specify only the IP address not DNS name. Then I thought I can
use some Linux machine to forward those packets to a dynamic domain
(somewhere in internet)... I'm sure it is possible but the question
remains the same - how ?

There's one more thing - a software that I want to redirect packets to
also sends confirmation to the device so all the packets have to have
source IP address of my device not the gateway.

I suppose it may be not clear what I'm trying to do, maybe someone
will understand my english

TroLoo