public static InetAddress[] getAllByName(String host) throws UnknownHostException

public static InetAddress getByName(String host) throws UnknownHostException

public String getHostAddress()

public String getHostName()

package java21;

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

/**
 * 2017/10/16
 * 说明：
 */
public class InetAddressDemo {
    public static void main(String[] args) throws UnknownHostException {
        InetAddress ip = InetAddress.getByName("www.baidu.com");

        System.out.print(ip.getHostName() +"\n"+ip.getHostAddress());

    }
}

public DatagramSocket(int port) throws SocketException

public void send(DatagramPacket p) throws IOException

public void receive(DatagramPacket p) throws IOException

public DatagramPacket(byte[] buf, int length, InetAddress address,int port)

public DatagramPacket(byte[] buf,  int length)

public InetAddress getAddress()

public byte[] getData()

public int getLength()

package java20;

import java.io.IOException;
import java.net.*;

/**
 * 2017/10/17
 * 说明：
 */
public class UDPSendDemo {
    public static void main(String[] args) throws IOException {
        DatagramSocket ds = new DatagramSocket();


        String str = "hello";

        DatagramPacket dp = new DatagramPacket(str.getBytes(),str.length(), InetAddress.getByName("127.0.0.1"),12345);


        ds.send(dp);

        ds.close();



    }
}

package java20;

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.SocketException;

/**
 * 2017/10/17
 * 说明：
 */
public class UDPReceiveDemo {

    public static void main(String[] args) throws IOException {
        DatagramSocket ds = new DatagramSocket(12345);

        byte[] buffer = new byte[1024];
        DatagramPacket dp = new DatagramPacket(buffer,buffer.length);

        ds.receive(dp);

        String ip = dp.getAddress().getHostAddress();
        String str = new String(dp.getData(),0,dp.getLength());
        int port = dp.getPort();

        System.out.println("ip地址："+ip);
        System.out.println("接收的内容："+str);
        System.out.println("端口号："+port);

        ds.close();



    }
}