UDP通信，消息传输的一个bug

[WZ22HAO]

a发给b str1 b接受到str1
b发给a str2 a接收到的是str1
b再发给a str3 a接受到str2
b发给a str4 a接受到str3

目前代码已经改好，但是不理解之前的问什么会出错
修改的方法：把UDP传送的报文分开定义，分别是msgPin和msgPout
注释掉的是原本有问题的代码

谢谢大家

//Client.java
import java.awt.BorderLayout;
import java.awt.Container;
import java.io.*;
import java.net.*;
import javax.swing.*;
import java.awt.event.*;

public class Client extends JFrame implements ActionListener, Runnable {
	private static final long serialVersionUID = 1L;
	final static int PC = 6000;
	final static int DESTINATION = 6001;
	final static String HOST = "127.0.0.1";
	final static int BUFFER_SIZE = 10000;
	String str;
	JPanel p;
	JButton btnSend;
	JTextField msgSend;
	JTextArea msgShow;
	//DatagramPacket msgP;
	DatagramPacket msgPin;
	DatagramPacket msgPout;
	DatagramSocket skt;
	InetAddress address;
	byte msg[] = new byte[BUFFER_SIZE];
	Thread thread;

	Client() {
		super("I am B");
		p = new JPanel();
		btnSend = new JButton("发送数据");
		msgSend = new JTextField(20);
		msgShow = new JTextArea(10, 10);
		p.add(msgSend);
		p.add(btnSend);
		Container con = getContentPane();
		con.setLayout(new BorderLayout());
		con.add(p, BorderLayout.NORTH);
		con.add(new JScrollPane(msgShow), BorderLayout.CENTER);
		btnSend.addActionListener(this);
		thread = new Thread(this);
		thread.start();
		setSize(400, 400);
		setVisible(true);
		setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
	}

	public void actionPerformed(ActionEvent e) {
		str = msgSend.getText().trim();
		if (str.length() != 0) {
			try {
				str = msgSend.getText();
				msg = str.getBytes();
				address = InetAddress.getByName(HOST);
				//msgP = new DatagramPacket(msg, msg.length, address, DESTINATION);
				//skt.send(msgP);
				msgPout = new DatagramPacket(msg, msg.length, address, DESTINATION);
				skt.send(msgPout);
				msgSend.setText("");
			} catch (IOException e1) {
				System.out.println("获取服务器失败");
			}
		}
		msgSend.setText("");
	}

	public void run() {
		try {
			//msgP = new DatagramPacket(msg, msg.length, address, PC);
			msgPin = new DatagramPacket(msg, msg.length, address, PC);
			skt = new DatagramSocket(PC);
		} catch (Exception e) {
			e.printStackTrace();
		}
		while (true) {
			if (skt == null) {
				break;
			} else {
				try {
					//skt.receive(msgP);
					//str = new String(msgP.getData(), 0, msgPin.getLength());
					skt.receive(msgPin);
					str = new String(msgPin.getData(), 0, msgPin.getLength());
					msgShow.append("收到数据" + str + "\n");
				} catch (Exception e) {
					e.printStackTrace();
				}
			}
		}
	}

	public static void main(String[] args) throws IOException {
		new Client();
	}
}

//Server.java
import java.awt.BorderLayout;
import java.awt.Container;
import java.io.*;
import java.net.*;
import javax.swing.*;
import java.awt.event.*;

public class Server extends JFrame implements ActionListener, Runnable {
	private static final long serialVersionUID = 1L;
	final static int PC = 6001;
	final static int DESTINATION = 6000;
	final static String HOST = "127.0.0.1";
	final static int BUFFER_SIZE = 10000;
	String str;
	JPanel p;
	JButton btnSend;
	JTextField msgSend;
	JTextArea msgShow;
	DatagramPacket msgPin;
	DatagramPacket msgPout;
	DatagramSocket skt;
	InetAddress address;
	byte msg[] = new byte[BUFFER_SIZE];
	Thread thread;

	Server() {
		super("I am A");
		p = new JPanel();
		btnSend = new JButton("发送数据");
		msgSend = new JTextField(20);
		msgShow = new JTextArea(10, 10);
		p.add(msgSend);
		p.add(btnSend);
		Container con = getContentPane();
		con.setLayout(new BorderLayout());
		con.add(p, BorderLayout.NORTH);
		con.add(new JScrollPane(msgShow), BorderLayout.CENTER);
		btnSend.addActionListener(this);
		thread = new Thread(this);
		thread.start();
		setSize(400, 400);
		setVisible(true);
		setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
	}

	public void actionPerformed(ActionEvent e) {
		str = msgSend.getText().trim();
		if (str.length() != 0) {
			try {
				str = msgSend.getText();
				msg = str.getBytes();
				address = InetAddress.getByName(HOST);
				//msgP = new DatagramPacket(msg, msg.length, address, DESTINATION);
				//skt.send(msgP);
				msgPout = new DatagramPacket(msg, msg.length, address, DESTINATION);
				skt.send(msgPout);
				msgSend.setText("");
			} catch (IOException e1) {
				System.out.println("获取服务器失败");
			}
		}
		msgSend.setText("");
	}

	public void run() {
		try {
			//msgP = new DatagramPacket(msg, msg.length, address, PC);
			msgPin = new DatagramPacket(msg, msg.length, address, PC);
			skt = new DatagramSocket(PC);
		} catch (Exception e) {
			e.printStackTrace();
		}
		while (true) {
			if (skt == null) {
				break;
			} else {
				try {
					//skt.receive(msgP);
					//str = new String(msgP.getData(), 0, msgPin.getLength());
					skt.receive(msgPin);
					str = new String(msgPin.getData(), 0, msgPin.getLength());
					msgShow.append("收到数据" + str + "\n");
				} catch (Exception e) {
					e.printStackTrace();
				}
			}
		}
	}

	public static void main(String[] args) throws IOException {
		new Server();
	}
}

[skgary]

DatagramPacket msgPin; DatagramPacket msgPout; 这几个变量应该放在thread类定义里，而不是放在client类里面。