Unable to access VPS using default port 4643

The corresponding VPS is unable to access using the http://:4643 is due to the configuration
setting OFFLINE_MANAGEMENT="no".

So to fix this issue:
1. Login into the Main VPS
2. cd /etc/sysconfig/vz-scripts
3. Find out the corresponding conf file of VEID (ie. if VEID is 437 then conf file is 437.conf)
4. Find out the entry OFFLINE_MANAGEMENT
5. modify it to OFFLINE_MANAGEMENT="yes"

OR

Run the following command after login into the main VPS.
vzctl set VEID --offline_management=yes --save

(example: vzctl set 353 --offline_management=yes --save)

This will fix the issue.

FTP not connecting with VE

You need to add rules in the IPtables to enable the FTP port.

Add the following lines in the /etc/sysconfig/iptables
-A VZ_INPUT -p tcp -m tcp --dport 8000:8250 -j ACCEPT
-A VZ_INPUT -p udp -m udp --dport 8000:8250 -j ACCEPT
-A VZ_INPUT -p tcp -m tcp --dport 21 -j ACCEPT
-A VZ_INPUT -p tcp -m tcp --dport 20 -j ACCEPT

service iptables restart

Here the ports 8000, 8250 are the passive ports.

I have done this fix in the Plesk VPS