Modified netcat command to work on OSX

[Mark Moran]

nc -l localhost 2001 works, while nc -l -p 2001 gave me: nc: missing port with option -l

[Alex Phenom]

@disccomp thanks for the correction!

[Ruben Kostandyan]

For me nc -l 2001 worked, without writing localhost.

[Ilya Panin]

According to command line help (-h):
-p port Specify local port for remote connects (cannot use with -l)