IP地址

1.网络中设备的标识
2.不易记忆，可用主机名
3.本地回环地址：127.0.0.1，主机名：localhost

端口号

1.用于标识进程的逻辑地址，不同进程的标识
2.有效端口：0_{65535，其中0}1024系统使用或者保留端口

传输协议

1.通讯的规则
2.常见协议：TCP，UDP

import java.net.InetAddress;
import java.net.UnknownHostException;

public class IPDemo {

    public static void main(String[] args) {
        InetAddress ia;
        try {
            ia = InetAddress.getLocalHost();
            System.out.println(ia.toString());
            System.out.println("address: " + ia.getHostAddress());
            System.out.println("hostName:" + ia.getHostName());

            ia = InetAddress.getByName("www.baidu.com");
            System.out.println("address: " + ia.getHostAddress());
            System.out.println("hostName:" + ia.getHostName());

        } catch (UnknownHostException e) {
            e.printStackTrace();
        }
    }

}