In general, FTP uses TCP port 20 as date port and TCP port 21 as command port. However, the data port is not always on port 20 and it depends on the
mode of FTP connection.
FTP can be run in active or passive mode. Would you please tell us which mode you were running?
If the client is behind a firewall and unable to accept incoming TCP connections, Passive mode would be a better option. In these scenario, you need
to set a passive port range as a passive mode FTP uses port 21 and a data port above 1023 port.
You can refer to the video and links below:
How to install and configure FTP on IIS 8 in Windows Server 2012
Microsoft is providing this information as a convenience to you. The sites are not controlled by Microsoft. Microsoft cannot make any representations regarding the quality, safety, or suitability of any software or information found there. Please make sure
that you completely understand the risk before retrieving any suggestions from the above link.
Microsoft is conducting an online survey to understand your opinion of the Technet Web site. If you choose to participate, the online survey will be presented to you when you leave the Technet Web site.