I have to thank Brian from Oracle support for this one, but let me first give you the story.
If you are trying to debug PL/SQL using Oracle SQLDeveloper 1.5.1 and getting an like this :
then you are probably facing one of two options :
You are trying to access you database server from a machine getting
its address from DHCP. In that case you will need to supply your ip
address each time your start a debugging session.
This is accomplished by checking the
Prompt for Debugger Host for Database debuggingcheckbox in the Debuger page of the preferences dialog as shown in the image below.
The other option is that your machine firewall is blocking access to
the debugging process between your machine and the DB server.
In that case you need to reconfigure SQL Developer to use a speciffic
port range and also have the firewall allow traffic through these
In my case all I had to do was change my debugger preferences so the dialog page looks exactly like this :
and also change my firewall setup to allow access through port 4000.
One final comment. When I run into this problem and asked for help, deep inside I was already blaming my unsupported CentOS Linux version. I had already run into the same problem with my openSUSE machine and found no way out. As it turned out the solution was not machine or distro specific but rather platform independent. So next time, I promise to have a little more faith in my own devices,
Now SQLDeveloper 1.5.1 runs very nicely on both machines at home and at work, and me having regained my trust on the platform, I even run it using the 64 bit 1.6.0_06 JDK. To be honest I haven't seen any real changes in terms of speed, but I tell myself that now I can savour one more taste of the 64 bit glamour. ;-)
Thanks again Brian.