经实践，可行的一篇文章分享：
https://blog.csdn.net/shile/article/details/74392125
主要点子：
1、Passive mode settings的use custom port range 设置为50000到50002
2、frpc配置
[ftp21] type = tcp local_ip = 127.0.0.1 local_port = 21 remote_port = 2121 [ftp1] type = tcp local_ip = 127.0.0.1 local_port = 50000 remote_port = 50000 [ftp2] type = tcp local_ip = 127.0.0.1 local_port = 50001 remote_port = 50001 [ftp3] type = tcp local_ip = 127.0.0.1 local_port = 50002 remote_port = 50002
注意这里一定有四个，不然列表会报425的错误。