After installing the File Transfer Pack on one of our servers for testing, I attempted to run my C# application but was unable to connect to the server using FTPS on the Internet (meanwhile, the same program worked flawlessly from my workstation). When connecting to a non-secured local FTP server, I had no trouble.
After some investigation, one of our network admins discovered that a connection to port 80 was attempted for the following IPs when connecting to the external FTPS server:
We block port 80 outbound for our internal servers, so this failed. I had him open port 80 for this server briefly, and my application executed successfully. He then restored the original configuration (blocking port 80), and my application once again succeeded. So it appears that this is only required on the first usage of the FTPS components.
We could not find any information on these IPs and they are not associated with the FTPS server the application is connecting to. What is the purpose of the activity that we observed? It appears that we will have to open port 80 temporarily for each server we use the components on for that first usage to contact those servers.