I have recently setup vsftpd to listen on port 990 for FTP over explicit SSL. I know from the RFCs that 990 is normally used for implicit. However, we have other FTPS servers accessed from the Internet via a single IP with NAT with static port forwarding. As far as I know this means we need to use different port number for each FTPS server daemon run from a different machine (physical/virtual etc).

Many FTP client programs support manual specification of which port to connect to and which mode to connect with i.e. implicit/versus explicit.

i.e. CuteFTP works fine, ftp-ssl on debian works fine.

However I have come across a couple of FTP clients such as FTP On the Go PRO for iPhone that are set to do implicit mode on ports 990/989 and explicit mode on the default FTP ports 21/20.

FTP On the Go PRO developers have so far refused to build in an option to allow explicit mode FTP on port 990/989 - and do not acknowledge the NAT and port forwarding issue.

This has lead me to ask the question: is there anything fundamentally wrong with an App supporting FTPES on ports 990/989?

My arguement is that one should be able to configure the client to connect to whichever port works.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Browse other questions tagged or ask your own question.