Unable to connect to FTP server using Filezilla with router in-between

Question

While connecting to my web server using filezilla, i am getting this error:

Status: Resolving address of ftp.mysite.org.in
Status: Connecting to 199.199.199.18:21...
Status: Connection established, waiting for welcome message...
Response:   220---------- Welcome to Pure-FTPd [privsep] [TLS] ----------
Response:   220-You are user number 1 of 150 allowed.
Response:   220-Local time is now 17:58. Server port: 21.
Response:   220-This is a private system - No anonymous login
Response:   220-IPv6 connections are also welcome on this server.
Response:   220 You will be disconnected after 5 minutes of inactivity.
Command:    AUTH TLS
Response:   234 AUTH TLS OK.
Status: Initializing TLS...
Error:  GnuTLS error -9: A TLS packet with unexpected length was received.
Status: Server did not properly shut down TLS connection
Error:  Could not connect to server

I use a cradlepoint CTR35 wifi router to connect to the wired internet connection. When i connect to the same server without this router, the connection works flawlessly.

So i guess there is some problem with my router firewall settings, but i dont know what! Can somebody help me out please?

Note: The server requires EXPLICIT FTP OVER TLS and does not work with plain FTP sessions. And i can connect to other servers using plain FTP with the router in between.

EDIT:

Okay. here is some debug info..

Status: Resolving address of ftp.md-47.webhostbox.net
Status: Connecting to 199.79.63.83:21...
Status: Connection established, waiting for welcome message...
Trace:  CFtpControlSocket::OnReceive()
Response:   220---------- Welcome to Pure-FTPd [privsep] [TLS] ----------
Response:   220-You are user number 1 of 150 allowed.
Response:   220-Local time is now 05:11. Server port: 21.
Response:   220-This is a private system - No anonymous login
Response:   220-IPv6 connections are also welcome on this server.
Response:   220 You will be disconnected after 5 minutes of inactivity.
Trace:  CFtpControlSocket::SendNextCommand()
Command:    AUTH TLS
Trace:  CFtpControlSocket::OnReceive()
Response:   234 AUTH TLS OK.
Status: Initializing TLS...
Trace:  CTlsSocket::Handshake()
Trace:  CTlsSocket::ContinueHandshake()
Trace:  CTlsSocket::ContinueHandshake()
Trace:  CTlsSocket::ContinueHandshake()
Error:  GnuTLS error -9: A TLS packet with unexpected length was received.
Status: Server did not properly shut down TLS connection
Trace:  CTlsSocket::OnSocketEvent(): close event received
Trace:  CRealControlSocket::OnClose(10053)
Trace:  CFtpControlSocket::ResetOperation(66)
Trace:  CControlSocket::ResetOperation(66)
Error:  Could not connect to server
Status: Waiting to retry...

Answer 1

Which mode have you got FileZilla setup for, Active or Passive?

Active doesn't work (easily) behind a NAT router.

For more info, see the FileZila wiki entry here:

Active mode

In active mode, the client opens a socket and waits for the server to establish the transfer connection. By default, FileZilla Client asks the operating system for the machine's IP address and for the number of a free port. This configuration can only work if you are connected to the internet directly without any NAT router, and if you have set your firewall to allow incoming connections on all ports greater than 1024.