Thank you very much for explanation.
I think it is the 1st case.
The reason I was asking this question is because when invoke http://mydomain - tomcat Bitnami shows the home page of tomcat without showing the port 8080.
I should know better to netstat to check the serving port!! But instead I checked all the config files in tomcat and see port 808!! I think tomcat Bitnami is using aliasing to hid the port 8080 from showing in url??
Thanks very much. I now know about case one and I am very happy to learn that.