I suddenly get this error using SFTP:

Status: Connecting to example.com...
Response:    fzSftp started
Command: open "[email protected]" 22
Command: Pass: *********
Status: Connected to example.com
Status: Retrieving directory listing...
Command: pwd
Response: Current directory is: "/root"
Command: ls
Status: Listing directory /root
Error: Connection timed out
Error: Failed to retrieve directory listing

I tried using FileZila, Cyberduck, Shell (Terminal), same result. However, it worked fine today (just a few seconds) in Passive mode.

I guess something changed in my network, so I have tried both: Active and Passive mode:

Connecting to probe.filezilla-project.org
Response: 220 FZ router and firewall tester ready
USER FileZilla
Response: 331 Give any password.
PASS 3.6.0.2
Response: 230 logged on.
Checking for correct external IP address
Retrieving external IP address from http://checkip.dyndns.org:8245/
Checking for correct external IP address
IP <external IP> big-bf-ccc-f
Response: 200 OK
PREP 49565
Response: 200 Using port 49565, data token 380352881
PORT 186,15,222,5,193,157
Response: 200 PORT command successful
LIST
Response: 150 opening data connection
Response: 503 Failure of data connection.
Server sent unexpected reply.
Connection closed

Because I'm working behind a router, I get my external IP from http://checkip.dyndns.org:8245/

I also tested different range of ports.