Hi Dain,
I had another look. Seems like the SSL connection is not closed properly.
netstat showed the following:
TCP SoapUITest:1389 SoapUITest.groupinfra.com:9091 CLOSE_WAIT
TCP SoapUITest:9091 SoapUITest.groupinfra.com:1389 FIN_WAIT_2
port 9091 is my SSL port.
It takes a while (1 or 2 minutes on my PC) before the port goes to status CLOSE_WAIT, and even then it does not work.
When the NullPointerException occurs, soapUI enters a state in which it is not possible anymore to use the mock service (no listener is started anymore on the mock SSL port), unless you restart soapUI entirely.
Regards,
Peter