FTP clients are considered to be rather temporary. Thus, they are only started and stopped during runtime and cannot be started at application startup. The FTP client API is designed to allow some functions to return intermediate results. This implies that only the process that started the FTP client can access it with preserved sane semantics. If the process that started the FTP session dies, the FTP client process terminates.
The client supports IPv6 as long as the underlying mechanisms also do so.