Java Process Not Terminating

I have a Java application launched via Webstart. About half the time, this program will not die. This program listens on a socket and when it receives a particular command, should close down. When it receives this command, it prints out what it normally should to the java console (that it received the shutdown command), the Java console closes, all the windows close, but the java process continues to run.

I have tried switching System.exit(0) to Runtime.getRuntime().halt(0) with no success - the same problem happens (my initial thought was a shutdown hook was affecting it).

Furthermore, when I have VisualVM connected to the Java process, it also indicates that it loses the connection when halt or exit are called, and I cannot reconnect, but the java process continues to exist.

Any ideas on how I could solve this? I've tries wrapping the program in try { } and exit/halt in finally { } to ensure nothing was holding it up, tried halting instead of exiting, etc...

My only thought is Java could be retaining a system resource (file handle to socket or something) or be stuck in a system call so the system won't let it quit - but the Java cons开发者_开发技巧ole closes, which to me seems like an indication the VM is trying to shutdown...

Any thoughts or ideas are appreciated!