Annoying bind exception...
If it looks like :

java.net.BindException: Address already in use

Then you might start your inquiry with the following command :

Windows : netstat -nab

OSX / Unix : lsof -i :9000

And...

WTF, Firefox (might be Windows though) is responsible for the port occupation. Shut down Firefox, kill the annoying issue !

-> lsof == list open files -> man lsof