Hi there. Again a quick one.
I had some problem with java on Debian. My Minecraft server started broadcasting only on ipv6.
I needed to change that.
I found two solutions:
1. for the hole system to use only ipv4. Look here.
2. Add one line of code, to user ./bash_profile or ./profile file in home dir
To force java to run only ipv4, add this line of code to your ./bash_profile or ./profile fine in your home dir (command mode)