When SQL Developer is idle I lose my connection

Question

My problem is this: I am running Oracle 10G on windows 98 on a virtual machine using VMWare on my desktop computer. I can connect to several users (SYS, HR, OE, ... ) with

Answer 1

This extension works for SQL Developer 4:

https://github.com/scristalli/SQL-Developer-4-keepalive

DISCLAIMER: I'm the developer of the extension. I hope the answer is not considered advertising, because this extension is open source (and the previous non-open-source extensions were accepted as an answer).