Solution where ftp suddenly fails to connect directly

Ideas:

1. Is the selinux problem on
2. Whether ftp port is included in iptbales
3. Whether FTP is enabled or not

Find command:

1. cat: /etc/selinux/config
See if SELINUX = disable is turned off

2, cat/etc/sysconfig/iptables
Check whether the firewall has the ftp specified port open

3,
1) command: getsebool ftpd_disable_trans can view the current state if not on
2) enter command: setsebool ftpd_disable_trans 1
You can also add the -P parameter so that you don't have to type this command every time you boot up
setsebool -P ftpd_disable_trans 1

Finally, the state of ftp is found to be on, open, ftp can be connected.