[2.1 IP通信](2.1IP%E9%80%9A%E4%BF%A1.md) [2.2 TCP特点和应用](2.2TCP%E7%89%B9%E7%82%B9%E5%92%8C%E5%BA%94%E7%94%A8.md) [2.3 实例](2.3%E5%AE%9E%E4%BE%8B.md)