import java.io.IOException;

import java.net.DatagramPacket;

import java.net.DatagramSocket;

import java.net.InetAddress;

import java.net.SocketException;

import java.net.UnknownHostException;

public class LoginClient {

	public static void main(String[] args) {

		String info = "你好，我想咨询一个问题";

		byte[] infos = info.getBytes();

		//IP地址获取方法

		InetAddress ia;

		DatagramSocket socket =null;

		try {

			ia = InetAddress.getByName("localhost");

			DatagramPacket dp = new DatagramPacket(infos, infos.length, ia, 5000);

			socket = new DatagramSocket();

			socket.send(dp);

			//接收服务端信息

			byte[] replys = new byte[1024];

			DatagramPacket dp1 = new DatagramPacket(replys,replys.length);

			socket.receive(dp1);

			String reply = new String(dp1.getData(),0,dp1.getData().length);

			System.out.println("服务器说："+reply);

		} catch (UnknownHostException e) {

			e.printStackTrace();

		} catch (SocketException e) {

			e.printStackTrace();

		} catch (IOException e) {

			e.printStackTrace();

		}finally{

			socket.close();

		}

	}

}

import java.io.IOException;

import java.net.DatagramPacket;

import java.net.DatagramSocket;

import java.net.SocketAddress;

import java.net.SocketException;

public class LoginService {

    public static void main(String[] args) {

        DatagramSocket socket = null;

        byte[] info = new byte[1024];

        DatagramPacket dp = new DatagramPacket(info, info.length);

        try {

            socket = new DatagramSocket(5000);

            socket.receive(dp);

            String infos = new String(dp.getData(), 0, dp.getData().length);

            System.out.println("客户端说："+infos);

            //给客户端一个响应

            String reply = "你好，有什么问题请说";

            SocketAddress sa = dp.getSocketAddress();

            DatagramPacket dp1 = new DatagramPacket(reply.getBytes(), 0, reply.getBytes().length, sa);

            socket.send(dp1);

        } catch (SocketException e) {

            e.printStackTrace();

        } catch (IOException e) {

            e.printStackTrace();

        }finally{

            socket.close();

        }

    }

}