参考资料:
(1)程序员面试被问到“三次握手,四次挥手”怎么办?
https://blog.csdn.net/csdnnews/article/details/86570658
(2)TCP三次握手的思考,为什么要有三次握手?
https://blog.csdn.net/whyliyu/article/details/51078276
https://blog.csdn.net/csdnnews/article/details/86570658
https://blog.csdn.net/whyliyu/article/details/51078276