远程登录到服务器，执行dir/ls等命令，一律是：
ftp> ls
500 Illegal PORT command.
ftp> dir
500 Illegal PORT command.
服务器有问题？上网搜索，很多人都人云亦云，自己都没试用。找了半天，终于找到了一个解决办法。即使用quote/passive更改模式：
ftp> quote pasv
227 Entering Passive Mode (192,168,2,2,1111,5555)
ftp> passive
Passive mode on.
ftp> dir
227 Entering Passive Mode (192,168,2,3,117,56)
150 Here comes the directory listing.
drwxr-xr-x 9 0 0 220 Sep 16 2019 apache-tomcat-8.5.46
drwxr-x--- 3 0 0 18 Nov 20 2020 apache-tomcat-home
drwxr-xr-x 9 0 0 202 Aug 19 2020 apache-tomcat-plugin_test
drwxr-xr-x 9 0 0 220 Jul 03 2020 apache-tomcat-reader
drwxrwxr-x 9 1123 1123 220 Aug 12 2020 apache-tomcat-temp-test
drwxr-xr-x 9 0 0 220 Jul 03 2020 apache-tomcat-upgrade
drwxr-x--- 3 0 0 18 Nov 20 2020 apache-tomcat-wo
226 Directory send OK.
