一、select
二、poll
三、epoll
1.epoll的优点与缺点
https://www.cnblogs.com/ftl1012/p/9384449.html
https://www.cnblogs.com/aspirant/p/9166944.html
https://www.sooele.com/1410.html
https://www.jb51.net/article/111899.htm
https://www.linuxidc.com/Linux/2017-09/146988.htm
https://www.cnblogs.com/JohnABC/p/6076006.html
https://blog.csdn.net/zhuangzi123456/article/details/84400108
https://blog.csdn.net/wuchuanpingstone/article/details/82964256