On probably 9 out of 10 support calls for FTP, the root cause is a customer or customer counterparty's corporate or network firewall. FTP is very commonly blocked by firewalls, and often firewall changes can introduce new blocks that didn't previously exist. Furthermore, FTP has two separate modes, Passive and Active mode, which can interact with firewalls in unpredictable ways.

The approach should be to find a set of settings that will work for a particular network/firewall. This may vary across your user base depending on what corporate or network firewalls they find themselves behind.

Manually Whitelisted IP Addresses

Have you manually whitelisted any IP addresses anywhere? If so, verify that all of the appropriate IPs are whitelisted, not just some of them.

If your site uses a custom domain, you have two dedicated IPs that need to be whitelisted in your firewall. You can find your dedicated IPs on the Firewall page of your site. If you have a custom domain, you also need to ensure that you are connecting to it, and not to [your_subdomain].files.com.

If you do not have a custom domain, ensure that our main IPs on this list are whitelisted, not just some of them. There are quite a lot of IPs on that list (over 80 at last count) and you need to whitelist all IPs or else you will experience failures. If whitelisting that many IP addresses is a problem for you, the solution is to move to a custom domain. This will get you a pair of IP addresses you can whitelist.

See If You Need To Ask For An IP Whitelist

If you have not whitelisted IP addresses, maybe your firewall administrator requires this for FTP traffic. Please submit a request to your network or firewall administrator to allow FTP port 21 and 40000-50000 traffic to all of the IPs on this list. If your firewall team does not allow whitelisting port 21 traffic, ask for port 3021 instead.

Try Other Ports

By default, FTP is used on port 21. Files.com also supports 990, 3021, and 3990 as alternate ports. Many firewalls will allow traffic on port 3021 despite blocking it on port 21. We recommend testing this next if you have exhausted other firewall issues. In many cases, simply using the alternate port will get your corporate firewall to let the connection through.

Active vs Passive Mode

Try toggling Active/Passive mode. Many FTP clients offer a choice of Active Mode vs Passive Mode. Files.com supports both, but your corporate or network firewall might block one or the other. We recommend testing both options in conjunction with testing the alternate ports in the above step.

Files.com recommends using Passive mode for all FTP and FTPS connections.