linux - Used/blocked ports in Ubuntu

starting up Glassfish AS would tell me the port 4848 is blocked (or any port that I configure). But checking the ports are not used. There is no firewall.

root@ubuntu:~/glassfishv3/glassfish/bin# netstat -tlunp

Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address           Foreign Address         State       PID/Program name
tcp        0      0 0.0.0.0:22              0.0.0.0:*               LISTEN      2149/sshd       
tcp        0      0 127.0.0.1:631           0.0.0.0:*               LISTEN      2441/cupsd      
tcp        0      0 0.0.0.0:5432            0.0.0.0:*               LISTEN      2075/postgres   
tcp6       0      0 :::22                   :::*                    LISTEN      2149/sshd       
tcp6       0      0 :::5432                 :::*                    LISTEN      2075/postgres   
udp        0      0 0.0.0.0:68              0.0.0.0:*                           2082/dhclient3  
udp        0      0 0.0.0.0:39256           0.0.0.0:*                           2413/avahi-daemon: 
udp        0      0 0.0.0.0:5353            0.0.0.0:*                           2413/avahi-daemon: 

Ubuntu 9.04 Linux ubuntu 2.6.28-11-generic #42-Ubuntu SMP Fri Apr 17 01:58:03 UTC 2009 x86_64 GNU/Linux (its a virtual server hough).

Not quite sure how to approach this problem.