启动流程和接收消息：
https://blog.csdn.net/weixin_41385912/article/details/110944462
netty结构和线程模型，以及java原生bio、nio的demo：
https://mp.weixin.qq.com/s?__biz=MzI5MTU1MzM3MQ%3D%3D&chksm=ec0fb874db783162d60a288a1b4e4ef008852d773693a77bfc58608fae380fd0a14a40e96195&idx=1&mid=2247487808&scene=21&sn=043e5e674b798d0f02d13639cba547b6