I tried to use explicit TLS encryption for FTP and it did not work so well. I am behind a firewall that blocks all unsolicited inbounds. However, I also tested it on two computers that are directly connected to the Internet. Here's the not-error msg:
Connected to server85.totalchoicehosting.com server85.totalchoicehosting.com
220-This computer system is for authorized users only. Individuals using this
220 ProFTPD 1.2.10 Server (ProFTPD) [66.235.180.4]
234 AUTH TLS-P successful
starting SSL/TLS
secure protocol TLSv1 used.
(secure) User: -------
331 Password required for -------
(secure) Password: ************
230 User ------- logged in.
sslftp> passive
Passsive mode enabled
sslftp> debug
Debugging enabled
sslftp> ls
n=1 arg_str={} p[0]={ls} p[1]={(null)}
send 5,6> PASV
read 5> 227 Entering Passive Mode (66,235,180,4,181,210).
Passive mode connection to: (66.235.180.4) 46546
Connecting to remote system 66.235.180.4 46546 (passive mode)
send 5,8> NLST .
Opening 66.235.180.4 46546 (passive mode data channel)
And here's the error msg, after almost a minute:
Couldn't open data connection, Operation timed out
data connection failed, waiting on server response...
Same error on my home computer (Windows XP) and the two other directly connected computers (Unix). Similar error msg for explicit SSL.
I monitored my net connections and saw a SYN_SENT during the wait-time to the 66.235.180.4:46546 specified by server85. But server85 seemed to have rejected the connection.