To view the ports used by your current Oracle Application installation navigate to
OAM->Site Map->Hosts->View Configuration. It will show the list of ports. It is created during installation and saved as config.txt under $APPL_TOP. Typical values are like
Data Port 9100
Discoverer port 8000
FND Java Cache Port Range
Forms Servlet Port Range 18000-18009
iMeeting iMon port Monitor Port 9700
Java Object Cache Port 12345
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Web Cache HTTPS Port 8000
Web Cache Statistics Port 4002
Web SSL Port 443