Not able to use the get command, error: 421 Service not available, remote server has closed connection

So this doesn’t happen when I try to use vsftpd_v1 to execute, but I’m using xxx, and this error keeps showing up. I’m able to login to ftp, use “ls”, but the problem is the get command. Help me out here please

Please remember that some versions are faulty. Read through all the tasks, that will help. And don’t share details here.