参考网址：
https://blog.51cto.com/dreamway/1045610

关键的几个：

CWD：允许切换目录
DELE：允许删除文件
MKD：允许新建目录
PNFR、PNTO：允许重命名
STOR：允许上传
SITE：允许修改权限 （指windows资源管理器，右击属性改权限）

ABOR - abort a file transfer
CWD - change working directory
DELE - delete a remote file
LIST - list remote files
MDTM - return the modification time of a file
MKD - make a remote directory
NLST - name list of remote directory
PASS - send password
PASV - enter passive mode
PORT - open a data port
PWD - print working directory
QUIT - terminate the connection
RETR - retrieve a remote file
RMD - remove a remote directory
RNFR - rename from
RNTO - rename to
SITE - site-specific commands
SIZE - return the size of a file
STOR - store a file on the remote host
TYPE - set transfer type
USER - send username

ACCT - send account information
APPE - append to a remote file
CDUP - CWD to the parent of the current directory
HELP - return help on using the server
MODE - set transfer mode
NOOP - do nothing
REIN - reinitialize the connection
STAT - return server status
STOU - store a file uniquely
STRU - set file transfer structure
SYST - return system type