First of all Hello from Georgia (east Europe) 
And now about my question. I have Windows server 2012 and have FTP server. I used this tutorial and everything is very clear to understand:http://technet.microsoft.com/en-us/library/hh831655.aspx
So and now what is my problem. Me and my friend have one router. my friend already have Linux server and server Ip address is 192.168.1.100 port range: 1-1000. My server Ip address is 192.168.1.99 and port range: 1001-1100. As i said I installed ftp server
and everything works fine in local lan. for example:
ftp://192.168.1.99:1050 and I can enter here using username and password which i have or guest user but i can't use my ISP(external IP) ip address and this ftp port 1050 which I assigned my ftp server. for example 95.XX.104.XX:1050. browser loading and
after this page not found. This port ranges are open in router and works in local lan as i said. My problem is that i cant change ftp port from 20/21 to for example 1500/1501.
Also at this moment windows server firewall is disabled so this isn't a problem. I thin I must enter new ftp port somewhere to make working. I can't use port 20,21 so any idea how replace this default ftp ports with my new ports which i have in router. range 1001:1100
Thanks