Howdy! I'm not a Java coder, but I am a crusty old UDP & BSD kernel
code-whacker. To properly do UDP-based discovery in a BSD-based
networking stack (like OS X) , you need to send to the broadcast
address of each interface marked UP and BROADCAST by the kernel.
This will allow the kernel code to get the broadcast to each interface.
Sending to All-Ones Broadcast on a Berkeley-based network stack only
gets the message out the first discovered interface (by the Host Reqs RFC,
it's an stack implimentation decision what to do - pick one vs. flood to each
interface.)

I looked at the JEmplode source (20b13) and thought it was going to try to
do the Right Thing with it's interfaceToBroadcastAddress hashtable
(in org/jempeg/empeg/ protocol/NetworkEmpegDiscoverer.java) However,
on closer inspection, it's faking out b'cast net addresses by 1) assuming
8-bit subnet masks from all of the IP addresses it can get from Java. To
make matters worse, it gets the addresses from java by calling
InetAddress.getAllByName(), which (by looking at the J2SE v1.4.2 sources),
is returning the list of IP addresses associated with the HOSTNAME in
the various name services (i.e., host tables, DNS, etc).

Please don't take this as a knock of the JEmplode folks. I'm just trying to
explain what the JEmplode code is Really Doing vs. what it Needs To Do
for multiply-homed hosts. I have no idea how to get the real interface
info up into Java (heck, I don't even know how to create JAR files :-)

For some reason, I can't download the source for your app right now, so I
can't tell if you cloned that part of the code. I don't *think* you did, as I'm
having the same problem with my TiBook and airport card and the above
hack should work for my situation but I can't discover the Empeg with your
app. Is there any way to get to your Preferences settings with no Empeg
discovered?

The reason all the above sounds a little hand-wavy is my Mac's at home so
I can't test it right now. I'm at work avoiding working on multi-OS build
environments and distorting NMAKE into performing some unnatural acts...

Hope this helps,
K^2