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.

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.