[ale] "Too many open files" while opening a socket on Ubuntu

[JK]

I have a Java app that needs to open many many UDP sockets.  When
it's opened around 120 of them, further attempts fail with a
"Too many open files" exception.  It also starts a thread to handle
traffic on each of these sockets.  This error happens on Ubuntu 8.10,
but not on Fedora 8.

ulimit -a says both max user processes and max open files = 65000
(because I changed them in /etc/security/limits.conf). I mention
user processes because I know Linux threads are implemented as
kernel-level processes, so I thought that might be relevant.

Any ideas?  Google is leading me only to answers related to
ulimits.  It certainly seems to be a configuration issue with user
resource limits, but I don't see any obvious way to change (or
discover the values of) limits related to sockets.

I'd really hate to have to go back to Fedora to solve this :-(

Thanks,

-- JK


-- 
I do not particularly want to go where the money is -
  it usually does not smell nice there. -- A. Stepanov