I have an Odroid HC2 with OMV 4 installed. I have enabled FTP under Services, and have also created a certificate and enabled SSL/TLS connections. I intend to connect outside of my network. I followed these directions to have what I think are the right settings for FTP. I tried testing the connection with Filezilla installed on my laptop (on the same network with Odroid), and it authenticates fine, and I can even accept the certificate, but then I get the error, "The data connection could not be established: ECONNREFUSED - Connection refused by server."
I tried going to System > Network > Firewall and I created some Accept rules for port 21 and the passive ports (I had seen this post, and example_rules.jpg), but it makes no difference. I also have port 21 and the passive ports forwarded on my router. I get the same error locally. I tried connecting my laptop to a VPN outside of my network, and I am able to accept the certificate, but again, same error.
I honest to goodness have no idea what I'm doing. Please help.