I have a FTP server (vsftpd) setuped on a Linux box (Ubuntu server). When I try to connect with a computer on the same network everything works fine as expected.

But as soon the IP is external it won't connect..

I first assumed the port was blocked, but then:

localserver:$ sudo tail -f /var/log/vsftpd.log

Wed Jan 13 14:21:17 2010 [pid 2407] CONNECT: Client "xxx.xxx.107.4"

remotemachine:$ netcat svn-motion.no-ip.biz 21

220 FTP Server

And it hangs there ..

Is there any other ports other than 21 that are required to be open ?