If you get this type of error message, please check the server's firewall first. I have faced this error message during connecting to the FTP server. In my case passive ports ranges were not enabled in the FTP and iptables firewall.
PassivePortRange 30000 50000
Add the above line in the ftp configuration file and enable them in the iptables like :
iptables -A INPUT -p tcp --destination-port 30000:50000 -j ACCEPT
iptables -A OUTPUT -p tcp --source-port 30000:50000 -j ACCEPT
Then restart iptables and ftp server like :
service iptables restart
If above solutions don't work please configure CSF+LFD firewall on the server and stop iptables. This will solve the problem.
Another important point is that you may connect to the server through "active mode [server will connect to the client]" through the FTP client(like filezilla). Just enable the option a the FTP client and retry to connect. That's it.