Algumas nc
versões têm -p
opção com significado diferente:
-p source_port
Specifies the source port nc should use, subject to privilege restrictions and availability. It is
an error to use this option in conjunction with the -l option.
enquanto outro:
-p port local port number (port numbers can be individual or ranges: lo-hi [inclusive])
No seu caso, basta usar nc -l 9999 > /dev/sdf
.