没有写界面，但是主要的代码都已经写出。

import java.io.*;import java.net.*;class ChatDemo{	public static void main(String [] args)throws Exception	{		DatagramSocket send1 = new DatagramSocket();		DatagramSocket rece1 = new DatagramSocket(10001);		new Thread(new send(send1)).start();		new Thread(new rece(rece1)).start();	}}class send implements Runnable  {	private DatagramSocket ds;	public send(DatagramSocket ds)	{		this.ds = ds;	}	public void run()	{		try		{			BufferedReader buf = new BufferedReader(new InputStreamReader(System.in));//读取键盘输入 			String line = null;			while((line = buf.readLine())!=null)//如果不为空，就继续读			{				byte [] b = line.getBytes();				DatagramPacket dp = new DatagramPacket(b,b.length,InetAddress.getByName("192.168.33.1"),10001);//构造数据包，发送到指定主机端口				ds.send(dp);			}			ds.close();		}		catch (Exception e)		{			throw new RuntimeException("发送端失败");		}	}}class rece implements Runnable{	private DatagramSocket ds;	public rece(DatagramSocket ds)	{		this.ds = ds;	}	public void run()	{		try		{			while(true)			{				byte [] b = new byte[1024*64];				DatagramPacket dp = new DatagramPacket(b,b.length);//接收发送过来的数据				ds.receive(dp);				String ip = dp.getAddress().getHostAddress();//读取IP				String data = new String(dp.getData(),0,dp.getLength());//读取数据				System.out.println(ip+":"+data);			}		}		catch (Exception e)		{			throw new RuntimeException("接收端失败");		}	}}