> I also already tried that to no avail...

Then either your database server is not running (or running on different
port, default is 3050), or your JVM is not allowed to connect to localhost.

> How would I do that? I never changed any security settings....

Check JDK/JRE documentation and/or your web server documentation. As a test
you can write small program that tries to connect to localhost on port 3050.

Roman