I've noticed the port
55555 looks like it is already in use on Mac OS Big Sur.
If you run
nc -l 55555 it shows an error.
Address already in use
But nothing answers if you telnet it, and nothing shows up on
lsof -i tcp:55555 too. Very odd behaviour.
Confirmed on several different machines.
Is there any way to figure out what is running and release it?