SOA Suite 11g Technology Preview 3 needs an Oracle database and Oracle XE (the free database edition) is ideal as the installation is so straight forward. By default the installation sets the database listener port to 1521 and the http server port to 8080. If these ports are already in use on your machine, the installer will prompt you to specify an available port number.
On a Windows XP installation the Oracle XE installer reports that a port is in use if that port number is being blocked by the firewall. Disabling the firewall is generally not a good idea as, along with anti-virus software, it provides a crucial defence for your machine, network and business.
The windows firewall settings can be found in the Control Panel. Just add the default port numbers to the firewall exception list. Once that is done, one can switch back to the ‘Choose Port’ dialog, put the default value in and continue with the Oracle XE installation.