Then I setup two ubunutu boxes with oracle java 11, one runing the author, and one runing the publisher. Author starts correctly on port 4502, but publisher starts incorrectly on port 4502 intstead of 4503.
The jar is called: /home/aem/publish/aem-publish-p4503.jar
When you run(double click) the jar file, it will read the the jar file name and will pick port number from file name itself. If you don't follow jar file naming conversion (-p4502/-p4503), if port 4502 is available then it will take port 4502.
If you are executing/running bath file, you should change the port explicitly by opening it in any text editor.
Update the CQ_PORT in start.bat/quickstart.bat before running it.