How to connect to FTP server when port 21 is blocked by my ISP?

Question

I am trying to connect to a shared hosting FTP server via port 21 but its blocked by my ISP. I'm using an internet dongle. I'm travelling and must use the dongle since there is no other wired internet or Wifi in this remote region. I contacted the host and they refuse to change the port for a single site. Port 990 is unavailable as my host offers FTPS on port 21 itself.

So how do I connect to an FTP server on port 21 when the port is blocked by my ISP? FTP Proxies? I have a locally setup Windows Server that I could install custom apps on.

Solution

The simplest way might be using a SSH tunnel through a server that has outgoing 21 open. (For details, see e.g. How to Use SSH Tunneling to Access Restricted Servers and Browse Securely.)

ssh -L 10021:ftp.example.com:21 [email protected]

or on Windows, with the same settings in PuTTY. Then connect using ftp://localhost:10021/.

If you don't have such intermediate server (SSH, VPN etc.) you actually need to use another port. If the FTPS is configured to use the same port 21, see if you can use SFTP that defaults to port 22 (as it uses SSH).