What would be the ip-address(source) in the packet.
Typically, once it leaves the WAN side of your router, the "source" address will be the router's external IP. The router itself, utilizing NAT will deal with the internal address of the return packets and send them to the appropriate port.
I said it before, I'll say it again.......do some research/reading on subnettting. Include NAT and "routing of packets" in your research.
When you say, "I have 2 devices (a switched HUB and a wireless router" I have to wonder what you mean by "a switched HUB".
That's an oxymoron.....or at the very least, a contradiction in terms.
A hub and a switch are physically similar (they both have RJ45 ports to plug network cables into), but in behaviour, completely different. There is no such thing as a "switched hub" A device is either a switch, or a hub but it cannot be both.
A quick google search of the two will tell you their differences and you'll understand why you can't have a "switched hub".
It matters not how straight the gate,
How charged with punishments the scroll,
I am the master of my fate;
I am the captain of my soul.