Since the method of setting FTP was complicated in the firewall settings, it is easy, but I summarized it. We hope that it will be useful to you when building and operating the environment.
It is a protocol for file sharing. One of the ports used when sharing files.
--Control connection (21 port) --Data connection (20 ports, random port)
Two modes of FTP
--Active mode --Passive mode
A session is held from the server to the client at the time of data connection. It is set by default on Windows.
Send: Client TCP 21 → Receive: Server TCP 21 Send: Server TCP 20 → Receive: Client TCP Random port
Session from client to server during data connection. It is set by default on Linux. Windows can change the passive mode, but it doesn't seem to work.
Send: Client TCP 21 → Receive: Server TCP 21 Send: Client TCP Random Port → Receive: Server TCP Random Port
The movement to connect with a control connection is basically the same. Just to use different modes in the data connection, random ports, The setting method may be different, or you may not be able to share files as you wish. Please refer to the above and enter the settings.