What do you mean by "not detected the lost of connection"? Does JBoss hang? Does the database call return immediately without any data?
If JBoss hangs, then it appears that the connection is not timing out. I believe that timing out a connection is a function of the socket layer, which is part of the operating system. Therefore you should post this question on the Unbuntu forum - how do you configure socket timeout.
In the truth the JBoss stay frozen and after 15 minutes it return with exceptions ( socket exceptions ) in the console.
But, in the Windows XP this not occurs.
Any idea ?
You need to ask on the Ubuntu forum how to set timeout on sockets.