Load Testing and BindException

Hello,

I am doing some simple Load Testing using SoapUI across to a Jax-ws/tomcat server. I am using the Simple strategy with 20 threads.

for some reason I see a:
17:47:39,023 ERROR [WsdlSubmit] Exception in request: java.lang.Exception: java.
net.BindException: Address already in use: connect

There is this nice link on this site:
http://www.eviware.com/content/view/65/44/
that explains how to modify the registry to get more client connections, etc.  but I can't see how I can possibly be running out of connections with only 20 threads?

Any ideas?

Also, it's my first time doing Load Testing/Test Suites with SoapUI and I just wanted to say what an awesome design on the steps, really liked it!!! 

thanks!