ICS vs INDY Listening on port difference

Hi

I'm passing messages using UDP and am in the process of changing from ICS to
INDY.
With ICS I could have several copies of the same app. all listening on the
same port using a plain TWSocket. With INDY using a TidUDPServer, as soon as
a second copy loads I get a port binding error.

So why can I have multiple listeners using one set of components and not the
other. Can I do anything with INDY components to allow multiple listeners on
the same port.

Thanks

Alan