I get connection refused when remotely debugging a Java application that executes on a different server. The JVM is version 16, and the OS is Ubuntu 21.04. I chose 8999 as an unused port on the server. Not much help from Oracle documentation on runjdwp.
The command line options are ...
-Xdebug \
-Xrunjdwp:transport=dt_socket,address=8999,server=y,suspend=y \