1.Check FTP settings are correct, the correct settings are as follows:
Enter filezilla configuration interface, click "setting" ,interface appears as follows:
Enter ilezilla configuration interface, click "users" ,interface appears as follows:
2.Check the server and the client whether there are safety devices, whether only open FTP single-port service (to communicate with the client, there are multiple hardware firewalls between the client and the server, only port 21 is open.)
Select 'Use custom port range' ,use a fixed port, such as 2000, and open the restriction of the port on the hardware firewall.