I made a JSP homepage file

The database and Tomcat are independent.

This means that you can run only the database, and you can run only Tomcat as well. No dependencies for each other.

Tomcat runs on A equipment (computer) and the database runs on B equipment, so JSP distributed on A equipment's Tomcat can access B equipment's database.

However, if you are an individual, you cannot leave A and B equipment on every day. That's why we use hosting services like dohome.

In other words, if you answer the question simply, there are firewall conditions, but you can post them on the homepage and connect to other databases.

You don't have to use only what dohome provides.(Of course, this is an exception if the firewall blocks the port.)