CPAN: https://perldotcom.perl5.cn/CPAN-local/
IO::SOCKET 模块: https://perldotcom.perl5.cn/CPAN-local/modules/by-module/IO/IO-1.20.tar.gz
RFC (请求注解) 端口分配: http://www.isi.edu/in-notes/iana/assignments/port-numbers