ftp 기본 함수 list
ftp_alloc / ftp_cdup / ftp_chdir / ftp_chmod / ftp_close / ftp_connect / ftp_delete
ftp_exec / ftp_fget/ ftp_fput / ftp_get_option / ftp_get / ftp_login / ftp_mdtm
ftp_mkdir / ftp_nb_continue / ftp_nb_fget / ftp_nb_fput / ftp_nb_get / ftp_nb_put
ftp_nlist / ftp_pasv / ftp_put / ftp_pwd / ftp_quit / ftp_raw / ftp_rawlist /ftp_rename ftp_rmdir / ftp_set_option / ftp_site / ftp_size / ftp_ssl_connect / ftp_systype