user@hostname:~$ ftp ftp.freebsd.org
ftp: connect to address 213.138.116.78: Connection refused
Trying 2001:41c8:112:8300::15:0...
ftp: connect: Network is unreachable
ftp>

user@yourmachine:~$ sudo apt-get install lftp

user@yourmachine:~$ lftp
lftp :~> set ftp:proxy http://proxyuser:proxypass@yourproxyIPorHOSTNAME:port
lftp :~> open ftp.example.com
lftp :~> USER ftpUSER
password: ftpPASS