I'm also having problems connecting to my FTP on a non standard port. I own a CS407 using firmware DSM 2.1-0839.
I already use port 21 for another FTP, so i have been trying to use different ports both active/passive modes to access my CS407, i have tryed port 81,82,83,84 and on some ports i get no connection, on port ex. 81 i can connect and it verifies my user/pass but cannont retrieve directory listing?
And yes i have forwarded the correct ports to my synology box, and veryfied that i can connect to my servers etc. from the outside, but not with the ftp service on my synology box?
Im totally blank on what to try? has anyone used the same synology box running a ftp service on a nonstandard port with succes?
Thanks in advance