Why is "nc -l xxxx" not opening a port?

I'm trying to get netcat to listen on port 4444, but it doesn't seem to be working. I am checking to see if the port is open using nmap, but it doesn't pick it up and I can't figure out why. I have tried various ports with no joy.

Here is a copy of my terminal so you can see what I am doing and what I have tried:

#iptables -L
Chain INPUT (policy ACCEPT)
target prot opt source destination
Chain FORWARD (policy ACCEPT)
target prot opt source destination
Chain OUTPUT (policy ACCEPT)
target prot opt source destination
# nmap localhost -p 4444
Starting Nmap 5.61TEST4 ( ) at 2012-07-31 16:37 BST
Nmap scan report for localhost (127.0.0.1)
Host is up (0.00019s latency).
Other addresses for localhost (not scanned): 127.0.0.1
PORT STATE SERVICE
4444/tcp closed krb524
Nmap done: 1 IP address (1 host up) scanned in 0.10 seconds
# nc -l 4444 &
[1] 1951
# nmap localhost -p 1-65535
Starting Nmap 5.61TEST4 ( ) at 2012-07-31 16:42 BST
Nmap scan report for localhost (127.0.0.1)
Host is up (0.0000070s latency).
Other addresses for localhost (not scanned): 127.0.0.1
Not shown: 65532 closed ports
PORT STATE SERVICE
22/tcp open ssh
7337/tcp open unknown
33507/tcp open unknown
Nmap done: 1 IP address (1 host up) scanned in 1.37 seconds
# ps -e | grep nc 12 ? 00:00:00 sync_supers 1156 tty1 00:00:00 ck-launch-sessi 1232 tty1 00:00:00 dbus-launch 1274 ? 00:00:00 klauncher 1951 pts/2 00:00:00 nc

1 Answer

I ran the verbose mode -v and got a clue back:

4444: inverse host lookup failed: Unknown server error : Connection timed out`
listening on [any] 41579 ...`

so I tried specifying a port with -p like this nc -lvp 4444 and it works:

listening on [any] 4444 ...

Obviously I need to use -p with -l with this version of nc.

I'd love it if anyone could tell my why there is this difference. Am I running an old version? (-h reports v1.10-38)