Error When Port Forwarding

[monomycelium]

I have a home Raspberry Pi, which I use as a NAS. The brilliantly-designed FDT is supercharged for transferring large files. Occasionally, I need to access those files when I am outside, using my Macintosh. I set up port forwarding for the ports 54321 and 43210 since I've noticed FDT uses them. However, the FDT server starts and stops with errors on my Raspberry Pi.

Details

2022-06-28 17:37:46 INFO lia.util.net.copy.FDT main 

FDT [ 0.26.3-202103312247 ] STARTED ... 


2022-06-28 17:37:46 INFO lia.util.net.common.Config <init> Using lia.util.net.copy.PosixFSFileChannelProviderFactory as FileChannelProviderFactory
2022-06-28 17:37:46 INFO lia.util.net.common.Config <init> FDT started in server mode
2022-06-28 17:37:46 INFO lia.util.net.copy.FDT main FDT uses *blocking* I/O mode.
2022-06-28 17:37:46 WARNING lia.util.net.copy.FDT main Failed to instantiate FDT
java.net.BindException: Address already in use
	at java.base/sun.nio.ch.Net.bind0(Native Method)
	at java.base/sun.nio.ch.Net.bind(Net.java:459)
	at java.base/sun.nio.ch.Net.bind(Net.java:448)
	at java.base/sun.nio.ch.ServerSocketChannelImpl.bind(ServerSocketChannelImpl.java:227)
	at java.base/sun.nio.ch.ServerSocketAdaptor.bind(ServerSocketAdaptor.java:80)
	at java.base/sun.nio.ch.ServerSocketAdaptor.bind(ServerSocketAdaptor.java:73)
	at lia.util.net.copy.FDTServer.<init>(FDTServer.java:67)
	at lia.util.net.copy.FDT.<init>(FDT.java:101)
	at lia.util.net.copy.FDT.main(FDT.java:467)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.base/java.lang.reflect.Method.invoke(Method.java:566)
	at lia.util.net.copy.FDTMain.main(FDTMain.java:55)

What ports should I set up for port forwarding? Should I enable mapping? Should I allow both the TCP and UDP protocols? I would appreciate any help.