根据个人理解写的，轻喷。

没什么大的逻辑，直接上代码。

UDPServer.java

package mySocket;

/*

* 服务器端

*/

import java.awt.GridLayout;

import java.io.IOException;

import java.net.DatagramPacket;

import java.net.DatagramSocket;

import java.net.SocketException;

import java.util.Vector;

import javax.swing.JFrame;

import javax.swing.JPanel;

import javax.swing.JScrollPane;

import javax.swing.JTextArea;

public class UDPServer extends JFrame{

static JTextArea textArea;

JPanel panel;

static Vector list = new Vector();

public UDPServer(){

this.setTitle("服务器端");

this.setLocation(100,100);

this.setSize(1100, 600);

this.setLayout(null);

this.setLayout(new GridLayout(1,2));

textArea = new JTextArea();

panel = new JPanel();

panel.setLayout(null);

textArea.setSize(this.getWidth()/2, this.getHeight());

panel.setSize(this.getWidth()/2, this.getHeight());

textArea.setEditable(false);

this.add(new JScrollPane(textArea));

this.add(panel);

this.setResizable(false);

this.setVisible(true);

this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

}

public static void main(String[] args) {

UDPServer UDPserver = new UDPServer();

textArea.append("***************************服务器已启动，"

+ "等待客户端的接入***************************\n");

try {

DatagramSocket server = new DatagramSocket(8888);

while (true) {

byte[] bytes = new byte[1024];

DatagramPacket packet = new DatagramPacket(bytes, bytes.length);

server.receive(packet);

UDPServerThread st = new UDPServerThread(server,bytes,packet,UDPserver,list);

st.start();

}

} catch (SocketException e) {

e.printStackTrace();

} catch (IOException e) {

e.printStackTrace();

}

}

}

UDPClient.java

package mySocket;

/*

* 客户端

*/

import java.awt.GridLayout;

import java.awt.event.ActionEvent;

import java.awt.event.ActionListener;

import java.awt.event.WindowAdapter;

import java.awt.event.WindowEvent;

import java.io.IOException;

import java.net.DatagramPacket;

import java.net.DatagramSocket;

import java.net.InetAddress;

import java.text.DateFormat;

import java.text.SimpleDateFormat;

import java.util.Arrays;

import java.util.Date;

import javax.swing.JButton;

import javax.swing.JFrame;

import javax.swing.JPanel;

import javax.swing.JScrollPane;

import javax.swing.JTextArea;

import javax.swing.JTextField;

public class UDPClient extends JFrame implements ActionListener{

static JTextArea textArea;

String username;

JPanel panel;

JTextField sendTextfield;

JButton button;

DatagramSocket client;

InetAddress address;

int port;

Date date;

DateFormat format = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");

String time;

public UDPClient(String username) throws Exception{

this.username = username;

this.setTitle("客户端");

this.setLocation(300,100);

this.setSize(400, 600);

panel = new JPanel();

textArea = new JTextArea();

sendTextfield = new JTextField(20);

button = new JButton("发送");

this.setLayout(new GridLayout(2, 1));

panel.setLayout(null);

textArea.setEditable(false);

sendTextfield.setBounds(0, 0, 200, 40);

button.setBounds(220, 0, 50, 40);

sendTextfield.setFocusable(true);

this.add(new JScrollPane(textArea));

panel.add(sendTextfield);

panel.add(button);

this.add(panel);

button.addActionListener(this);

this.setResizable(false);

this.setVisible(true);

this.addWindowListener(new WindowAdapter() {

public void windowClosing(WindowEvent e) {

date = new Date();

time = format.format(date);

byte[] data = ("-"+username).getBytes();

DatagramPacket packet = new DatagramPacket(data, data.length, address, port);

try {

client.send(packet);

} catch (IOException e1) {

e1.printStackTrace();

}

}

});

this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

client();

}

public void client() throws Exception{

/*

* 向服务器端发送数据

*/

// 1.定义服务器的地址，端口号，数据

address = InetAddress.getByName("localhost");

port = 8888;

date = new Date();

time = format.format(date);

client = new DatagramSocket();

byte[] data = ("用户 "+username+" 已加入(IP地址："+address.toString()+";端口号："+client.getLocalPort()+";时间："+time+")").getBytes();

// 2.创建数据报，包含了发送的信息

DatagramPacket packet = new DatagramPacket(data, data.length, address, port);

// 3.创建 DatagramSocket

// 4.向服务器端发送数据

client.send(packet);

byte[] bytes = new byte[1024];

UDPClientThread st = new UDPClientThread(client,bytes,packet,this);

st.start();

}

public void actionPerformed(ActionEvent e) {

JButton btn = (JButton)e.getSource();

if(btn==button){

String sendData = sendTextfield.getText();

sendTextfield.setText("");

if(!sendData.equals("")){

date = new Date();

time = format.format(date);

String CRCsendData = Arrays.toString(CRCCheck.getCRCByteValue(sendData.getBytes()));

byte[] data = ("^"+CRCsendData+"*"+username+"_"+sendData).getBytes();

DatagramPacket packet = new DatagramPacket(data, data.length, address, port);

try {

client.send(packet);

byte[] bytes = new byte[1024];

packet = new DatagramPacket(bytes, bytes.length);

// 2.接收服务器响应的数据

client.receive(packet);

// 3.读取数据

String reply = new String(bytes, 0, packet.getLength());

if(reply.equals("00000000")){

textArea.append("数据发送失败，请重新发送\n");

}else{

String username = reply.substring(0,reply.indexOf("_"));

String content = reply.substring(reply.indexOf("_")+1,reply.length());

textArea.append("用户 "+username+" 说："+content+"\n");

}

} catch (IOException e1) {

e1.printStackTrace();

}

}

}

}

}

UDPServerThread.java

package mySocket;

/*

* 服务器端线程

*/

import java.io.IOException;

import java.net.DatagramPacket;

import java.net.DatagramSocket;

import java.net.InetAddress;

import java.util.Arrays;

import java.util.Vector;

import javax.swing.JList;

public class UDPServerThread extends Thread {

DatagramSocket socket;

byte[] bytes;

DatagramPacket packet;

String info;

UDPServer UDPserver;

Vector list;

public UDPServerThread(DatagramSocket socket, byte[] bytes, DatagramPacket packet, UDPServer uDPserver, Vector list) {

this.socket = socket;

this.bytes = bytes;

this.packet = packet;

this.UDPserver = uDPserver;

this.list = list;

}

public void run() {

// 创建数据报，用于接收客户端发送的数据

try {

String sendData = null,username;

boolean isresponse = false;

// 读取数据

info = new String(bytes, 0, packet.getLength());

if(info.substring(0, 1).equals("-")){

username = info.substring(1);

list.remove(username);

UDPserver.textArea.append("用户 "+username+" 已断开连接\n");

}

else if(info.substring(0, 1).equals("^")){

isresponse = true;

String CRCinfo = info.substring(info.indexOf("^")+1,info.indexOf("*"));

String infoContent = info.substring(1).substring(info.indexOf("_"),info.length()-1);

String CRCcontent = Arrays.toString(CRCCheck.getCRCByteValue(infoContent.getBytes()));

UDPserver.textArea.append("客户端CRC校验码："+CRCinfo+"\n");

UDPserver.textArea.append("服务器端CRC校验码："+CRCcontent+"\n");

if(CRCinfo.equals(CRCcontent)){

UDPserver.textArea.append("匹配成功\n");

UDPserver.textArea.append(">>>>>用户 "+info.substring(info.indexOf("*")+1,info.indexOf("_"))+" 发送了一个数据包,内容为："+infoContent+"\n\n");

sendData = info.substring(info.indexOf("*")+1,info.indexOf("_"))+"_"+info.substring(1).substring(info.indexOf("_"),info.length()-1);

}else{

UDPserver.textArea.append("匹配失败\n");

sendData = "00000000";

}

}else{

isresponse = true;

username = info.substring(info.indexOf("户")+2, info.indexOf("已")-1);

list.add(username);

UDPserver.textArea.append(info+"\n");

sendData = "欢迎 "+info.substring(info.indexOf("户")+2, info.indexOf("已")-1)+" 加入";

}

UDPserver.panel.removeAll();

JList lists = new JList(list);

lists.setBounds(0, 0, 550, 600);

UDPserver.panel.add(lists);

UDPserver.panel.updateUI();

/*

* 响应客户端发来的消息

*/

// 1.定义客户端的地址，端口号，数据

if(isresponse){

InetAddress address = packet.getAddress();

int port = packet.getPort();

byte[] data = sendData.getBytes();

// 2.创建数据报，包含响应的数据信息

packet = new DatagramPacket(data, data.length, address, port);

// 3.响应客户端，发送数据

socket.send(packet);

}

} catch (IOException e) {

e.printStackTrace();

}

}

}

UDPClientThread.java

package mySocket;

/*

* 客户端线程类

*/

import java.io.IOException;

import java.net.DatagramPacket;

import java.net.DatagramSocket;

public class UDPClientThread extends Thread{

DatagramSocket client;

byte[] bytes;

DatagramPacket packet;

UDPClient udpClient;

public UDPClientThread(DatagramSocket client, byte[] bytes, DatagramPacket packet, UDPClient udpClient){

this.client = client;

this.bytes = bytes;

this.packet = packet;

this.udpClient = udpClient;

}

public void run(){

try {

packet = new DatagramPacket(bytes, bytes.length);

client.receive(packet);

} catch (IOException e) {

e.printStackTrace();

}

String reply = new String(bytes, 0, packet.getLength());

if(!reply.equals(""))

udpClient.textArea.append(reply+"\n");

}

}

CRCCheck.java

package mySocket;

import java.util.Arrays;

public class CRCCheck {

public static void main(String[] args) {

byte[] btm = new byte[] { 12, 13, 1, 0, 0, 1, 0, 31, -19, 0, 8,

0, 1 };

byte[] btl = CRCCheck.getCRCByteValue(btm);

System.out.println(Arrays.toString(btl));

byte[] testbyte = CRCCheck.getCRCByteValue("哈哈".getBytes());

byte[] testbyte2 = CRCCheck.getCRCByteValue("哈哈".getBytes());

System.out.println(Arrays.toString(testbyte));

System.out.println(Arrays.toString(testbyte2));

}

/**

* 入口方法

* @param bt 需要校验的字节流

* @return

*/

public static byte[] getCRCByteValue(byte[] bt){

char ch = caluCRC(bt);

return charToByte(ch);

}

publicstaticchar[] crc_tb= {

0x0000, 0x1021, 0x2042, 0x3063, 0x4084,

0x50a5, 0x60c6, 0x70e7, 0x8108, 0x9129, 0xa14a, 0xb16b, 0xc18c,

0xd1ad, 0xe1ce, 0xf1ef, 0x1231, 0x0210, 0x3273, 0x2252, 0x52b5,

0x4294, 0x72f7, 0x62d6, 0x9339, 0x8318, 0xb37b, 0xa35a, 0xd3bd,

0xc39c, 0xf3ff, 0xe3de, 0x2462, 0x3443, 0x0420, 0x1401, 0x64e6,

0x74c7, 0x44a4, 0x5485, 0xa56a, 0xb54b, 0x8528, 0x9509, 0xe5ee,

0xf5cf, 0xc5ac, 0xd58d, 0x3653, 0x2672, 0x1611, 0x0630, 0x76d7,

0x66f6, 0x5695, 0x46b4, 0xb75b, 0xa77a, 0x9719, 0x8738, 0xf7df,

0xe7fe, 0xd79d, 0xc7bc, 0x48c4, 0x58e5, 0x6886, 0x78a7, 0x0840,

0x1861, 0x2802, 0x3823, 0xc9cc, 0xd9ed, 0xe98e, 0xf9af, 0x8948,

0x9969, 0xa90a, 0xb92b, 0x5af5, 0x4ad4, 0x7ab7, 0x6a96, 0x1a71,

0x0a50, 0x3a33, 0x2a12, 0xdbfd, 0xcbdc, 0xfbbf, 0xeb9e, 0x9b79,

0x8b58, 0xbb3b, 0xab1a, 0x6ca6, 0x7c87, 0x4ce4, 0x5cc5, 0x2c22,

0x3c03, 0x0c60, 0x1c41, 0xedae, 0xfd8f, 0xcdec, 0xddcd, 0xad2a,

0xbd0b, 0x8d68, 0x9d49, 0x7e97, 0x6eb6, 0x5ed5, 0x4ef4, 0x3e13,

0x2e32, 0x1e51, 0x0e70, 0xff9f, 0xefbe, 0xdfdd, 0xcffc, 0xbf1b,

0xaf3a, 0x9f59, 0x8f78, 0x9188, 0x81a9, 0xb1ca, 0xa1eb, 0xd10c,

0xc12d, 0xf14e, 0xe16f, 0x1080, 0x00a1, 0x30c2, 0x20e3, 0x5004,

0x4025, 0x7046, 0x6067, 0x83b9, 0x9398, 0xa3fb, 0xb3da, 0xc33d,

0xd31c, 0xe37f, 0xf35e, 0x02b1, 0x1290, 0x22f3, 0x32d2, 0x4235,

0x5214, 0x6277, 0x7256, 0xb5ea, 0xa5cb, 0x95a8, 0x8589, 0xf56e,

0xe54f, 0xd52c, 0xc50d, 0x34e2, 0x24c3, 0x14a0, 0x0481, 0x7466,

0x6447, 0x5424, 0x4405, 0xa7db, 0xb7fa, 0x8799, 0x97b8, 0xe75f,

0xf77e, 0xc71d, 0xd73c, 0x26d3, 0x36f2, 0x0691, 0x16b0, 0x6657,

0x7676, 0x4615, 0x5634, 0xd94c, 0xc96d, 0xf90e, 0xe92f, 0x99c8,

0x89e9, 0xb98a, 0xa9ab, 0x5844, 0x4865, 0x7806, 0x6827, 0x18c0,

0x08e1, 0x3882, 0x28a3, 0xcb7d, 0xdb5c, 0xeb3f, 0xfb1e, 0x8bf9,

0x9bd8, 0xabbb, 0xbb9a, 0x4a75, 0x5a54, 0x6a37, 0x7a16, 0x0af1,

0x1ad0, 0x2ab3, 0x3a92, 0xfd2e, 0xed0f, 0xdd6c, 0xcd4d, 0xbdaa,

0xad8b, 0x9de8, 0x8dc9, 0x7c26, 0x6c07, 0x5c64, 0x4c45, 0x3ca2,

0x2c83, 0x1ce0, 0x0cc1, 0xef1f, 0xff3e, 0xcf5d, 0xdf7c, 0xaf9b,

0xbfba, 0x8fd9, 0x9ff8, 0x6e17, 0x7e36, 0x4e55, 0x5e74, 0x2e93,

0x3eb2, 0x0ed1, 0x1ef0

};

/**

* 获得CRC验证码

*/

publicstaticcharcaluCRC(byte[] pByte) {

int len = pByte.length;

char crc;

byte da;

crc = 0x0;

int i = 0;

while (len-- != 0) {

da = (byte) (crc / 256);

crc <<= 8;

int num = da ^ pByte[i];

if (num < 0)

num += 256;

crc ^= crc_tb[num];

++i;

}

returncrc;

}

/**

* char 转byte

*/

public static byte[] charToByte(char c) {

byte[] b = new byte[2];

b[0] = (byte) ((c & 0xFF00) >> 8);

b[1] = (byte) (c & 0xFF);

returnb;

}

}

/*用户登录界面，服务器运行状态下执行，客户端的main方法就在这个类里*/

User.java

package mySocket;

import java.awt.Color;

import java.awt.event.ActionEvent;

import java.awt.event.ActionListener;

import javax.swing.JButton;

import javax.swing.JFrame;

import javax.swing.JLabel;

import javax.swing.JPanel;

import javax.swing.JTextField;

/*

* 用户接入窗口类

*/

public class User extends JFrame implements ActionListener{

JPanel mainPanel;

JLabel userLabel,tipLabel;

JTextField userTextfield;

JButton loginBtn;

public User(){

this.setTitle("用户登录");

this.setLocation(300,100);

this.setSize(550, 600);

mainPanel = new JPanel();

userLabel = new JLabel("YourName:");

tipLabel = new JLabel("");

userTextfield = new JTextField(10);

loginBtn = new JButton("登入");

mainPanel.setBounds(0, 0, this.getWidth(), this.getHeight());

mainPanel.setLayout(null);

userLabel.setBounds(100, 200, 100, 20);

userTextfield.setBounds(210, 195, 150, 30);

tipLabel.setBounds(360, 200, 150, 20);

tipLabel.setForeground(Color.red);

loginBtn.setBounds(150, 250, 100, 20);

mainPanel.add(userLabel);

mainPanel.add(userTextfield);

mainPanel.add(tipLabel);

mainPanel.add(loginBtn);

this.add(mainPanel);

loginBtn.addActionListener(this);

this.setResizable(false);

this.setVisible(true);

this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

}

public static void main(String[] args) {

User user = new User();

}

public void actionPerformed(ActionEvent e) {

JButton btn = (JButton)e.getSource();

if(btn==loginBtn){

String username = userTextfield.getText();

if(username.equals("")){

tipLabel.setText("请输入一个名称！");

}else{

this.dispose();

try {

new UDPClient(username);

} catch (Exception e1) {

e1.printStackTrace();

}

}

}

}

}