When connecting to VPS via FTP( Say File zilla ) which results in Could not connect to server. But the settings will be perfect. You check with server FTP settings, Permissions, ports, FTP modes etc and see everything is fine.
After uploading large files via FTP connection in virtual servers (happens in normal Windows Physical servers too) the Gateway service which resulting the transactions hangs and can be restored only after reconnection.
The problem is caused and can be fixed by Application Layer Gateway Service.
Stop Application Layer Gateway Service and switch start up mode to Disabled or Restart the Application Layer Gateway service
Now the FTP connects as before.