can not access to FTP from remote, but it works from local

[legolas]

Hi
Thank you for reading my post
Local : computer that XAMPP is installed
Remote: computer that want to connect to XAMPP Server

I have installed XAMPP, now i also setup the FTP by adding user and groups.
problem is that i can access the FTP from local computer but there is no way to access to the computer from remote computers.
I also changed the IP bindings to only listen on 85.114.PPP.OOO and tried to access the ftp server from remote and it failed.

after i changed the IP binding i test it from local computer (computer that XAMPP is installed) using the server IP address and it works fine.
is there some setting that prevent accessing the FTP server from remote machines?

I should say that HTTP works fine.

[underdone]

Check to see that port 21 is open on the router, and you might have to set up 2 ports for passive mode too.

[legolas]

there is no port restriction in the server side because i am using port 81 for other purposes.
can you explain more about two ports and passive mode?
thanks.