[MxxCon]

on *nix systems ports 1-1024 are "privileged ports", meaning you need root account to access those ports, which is often not the case for ftp servers.
plus, you need to know how PORT or PASV(reply) commands are formed.
for example we have
PORT 192,168,150,80,14,178
obviously 192,168,150,80 are 8bit octets of your ip address.
14 and 178 are not plain port numers.
to find the actual port multiply the fifth octet by 256 and then add the sixth octet to the total. thus in the example above the port number is ( (14*256) + 178), or 3762.

and as you can image, the lowest valid PORT number you can have is x,x,x,x,1,1 or in other words 257