SolusVM system backup does not work: Connection timed out

Symptoms

SolusVM system backup does not work - the following error appears when the backup is started manually:

# php /usr/local/solusvm/system/systembackup.php
...
227 Entering Passive Mode (203,0,113,2,155,109)
Trying 203.0.113.2...
Connecting to 203.0.113.2 (203.0.113.2) port 49839
Connection timed out
Failed to connect to 203.0.113.2:49839; Connection timed out

Cause

Connection over passive ports is not allowed on the backup server.

Resolution

Allow connection over passive port range on the backup server - the required passive range can be found in the configuration of your FTP server - for example:

For proFTPd

For vsftpd