netstat '-' in pid column

[Brian McKee]

Hi All
     If you run sudo netstat -lnp you get a list of listening ports
(numerical) and the process id listening on that port.
e.g.
==> netstat -lnp
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address           Foreign Address
State       PID/Program name
tcp        0      0 0.0.0.0:4000            0.0.0.0:*
LISTEN      20116/rpc.statd
tcp        0      0 127.0.0.1:32768         0.0.0.0:*
LISTEN      3087/xinetd
tcp        0      0 0.0.0.0:32769           0.0.0.0:*
LISTEN      -

What does the '-' in the last row under process id mean?