Hi jcurtis,
I think you may want to create a Static Port Forward in the NR for Android and proxy the port from phone:2121 to ftp:2121.
FTP:localhost:4021 (using Dynamic Port Forward) => 10.0.0.4:21
FTP Data:localhost:
2121 (using Static Port Forward => 10.0.0.4:2121
1.Create the Static Port Forward:
localhost:2121 -> 10.0.0.4:2121
2.The settings on the Vsftpd seems good. As you did, it returns to ftp client with "227 Entering Passive Mode(127,0,0,1,8,73)", i.e. 127.0.0.1:2121. It tells your ftp client connect to localhost:2121, then gets forwarded to 10.0.0.4:2121. And because of this settings, your vsftpd already listens on 2121 and waiting for the data coming in.
Note:
1.Keep the command tunnel using port 21 and using the Dynamic Port Forward, as Android does not allow NR client to listen on a port <= 1024.
2.For the Static Port Forward, please refer to
http://www.neorouter.com/android/portforward.htmlLet us know if you still have problem.
Thanks,
KevinZ - NeoRouter team