Two servers (serverSocket) behind the SAME firewal !?l

Hello !
I dont know if this is the right forum for this qusetion,
and maybe the question is really stupid, but ...
I made a little client/server application, just to
play around with sockets and serverSockets.
It works fine, but now i ask myself:
What happens, if there are two of my servers running on two
different computers in the SAME LAN behind the SAME
firewall/internetgateway, and both are listening on the SAME
port ?
F.e. if the extern IP of this LAN/(its gateway) is
204.556.234.123, and a client in the internet is connecting
to it on the port, on which the two servers behind the firewall
are listening, WHO'S ANSWERING ?
(If this port is set to "open and forward" in the firewall)
The one with the shorter patch-cable ? ;)
How is it possible for the client to differenciate
this two servers in that LAN?
The only logical solution i found is that this two servers
have to listen on different ports,
but i think there has to be another explanation and/or solution.
Do i have to take care about situations like that in my
server-application ?
I have the feeling that i have to...somehow.
OK, you see i dont know much about this...
i would be very thankful for every hint and explanation.
Thank you very much,
greetings,
huni.

F.e. if the extern IP of this LAN/(its gateway) is
204.556.234.123, and a client in the internet is
connecting
to it on the port, on which the two servers behind the
firewall
are listening, WHO'S ANSWERING ?
(If this port is set to "open and forward" in the
firewall)Whichever one the firewall is told to forward it to!
The two computers running your server have unique addresses on the internal network. The firewall will forward incoming connections to one of those addresses. Maybe it can do some simple "load balancing" by forwarding some connections to one server and some to the other, but still, any particular connection will only go to one server.

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