I ran netcat server on knoppix 4.0 laptop and netcat client on a fedora core 5 laptop.
on the knoppix
nc -l 9000
on the fedora laptop
nc 192.x.x.x 9000

I didn't connect. There is no firewall on either my machines.
It worked among fedora laptops.

Even if i did ls.th ike this on the knoppix laptop and it still didn't work.
on one consle
nc -l 9000
on another console
nc localhost 9000

It said: "Knoppix 9000 (?) : Connection refused"

I checked iptables and it's all fine.

Please show some pointers.