参考博客:
互联网协议入门一:http://www.ruanyifeng.com/blog/2012/05/internet_protocol_suite_part_i.html
互联网协议入门二:http://www.ruanyifeng.com/blog/2012/06/internet_protocol_suite_part_ii.html
TCP/IP模型的一个简单解释:http://www.ruanyifeng.com/blog/2009/03/tcp-ip_model.html
TCP协议简介:http://www.ruanyifeng.com/blog/2017/06/tcp-protocol.html