关于心跳包的几个不错的内容

https://www.cnblogs.com/jarvise/p/4687950.html

http://www.voidcn.com/article/p-qtvcezwq-bry.html

数据库相关的：https://blog.csdn.net/linminqin/article/details/41115197

http://www.hongyanliren.com/2014m12/25700.html