I am using it.sauronsoftware.ftp4j with a cpanel server and when I try to close the connection, I am getting a 500 error: unknown command. I assume that means that the cpanel ftp server is using a different command but I don't know how to issue the proper command to close the ftp connection or even what that command is.
I am aware of abruptlyCloseCommunication() but I would prefer a clean and proper method for closing connections.
abruptlyCloseCommunication() method causes the communication channel to be abruptly closed. It is gives as an "emergency brake" to close the control connection when it is blocked. A thread-safe solution for the same purpose is a call to disconnect(false).
Instead you can use client.disconnect(true); class, This one sends the FTP QUIT command to the remote server, requesting a legal disconnect procedure. Hope it will also work for cpanel.