I’m not sure but I think the problem is that LeechFTP uses passive FTP mode (bot connections are established by client).
In this case:
1) client sends command PASV to server.
2) server start listening newly allocated port and responses with command PORT with its number.
3) client connects to this port => data channel is established.
I would recommend you to try some other FTP clients to check this issue, an example integrated into Windows http://ftp.exe. If I remember fine then explorer and IE also uses passive mode by default, but http://ftp.exe does not.