https://www.cnblogs.com/cmyxn/p/6360474.html
https://www.cnblogs.com/mike-mei/p/8548238.html
讲解Tomcat web容器运行
https://www.cnblogs.com/small-boy/p/8042860.html
长连接与短连接
https://www.cnblogs.com/gotodsp/p/6366163.html
https://blog.csdn.net/ideality_hunter/article/details/77712242
TCP包括长连接和短连接,UDP是无连接协议,只发包,ping就是UDP协议