-- FTP
-- localhost

How to test FTP connection to localhost in the rare case when the Unix box does not have ftp client installed?

The command line ftp client is quite common client, but in rare occasions it is not installed by default. Since installing additional software might require approvement and time, you could try using curl. For example, the following command connects, takes a list of files in the home folder and then closes the connection:

# curl -c /tmp/cookie --insecure -u <username>:<password> "ftp://<host>:<port>" -b /tmp/cookie

For more curl options you could refer to the curl man page.