A Server-FTP process SHOULD have an idle timeout, which will terminate the process and close the control connection if the server is inactive (i.e., no command or data transfer in progress) for a long period of time. The idle timeout time SHOULD be configurable, and the default should be at least 5 minutes.
A client FTP process ("User-PI" in RFC-959) will need timeouts on responses only if it is invoked from a program.
Without a timeout, a Server-FTP process may be left pending indefinitely if the corresponding client crashes without closing the control connection.