一.使用展示

1.运行代码，首选输入需要连接的局域网IP地址（不输入默认为本机127.0.0.1）

2.确定后进入聊天界面

这是System.out.println()打印的内容

?二.完整源代码(详细注解) 复制黏贴即可运行

import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.text.SimpleDateFormat;
import java.util.Date;

/**
 * @Author Student
 * @date 2021/8/10 8:34
 */
public class ChatUDPClient extends JFrame {
    public static void main(String[] args) {
        ChatUDPClient chatFrame = new ChatUDPClient();
    }

    private JTextField sendField;
    private JButton sendButton;
    private JTextArea msgArea;
    private StringBuilder stringBuilder;
    private SimpleDateFormat dateFormat;
    private JScrollPane scrollPane;
    private String ip;

    public ChatUDPClient() {
        //得到屏幕长宽，为了将界面置于桌面的中央
        int screenWidth = (int) this.getToolkit().getScreenSize().getWidth();
        int screenHeight = (int) this.getToolkit().getScreenSize().getHeight();
        int width = 320;
        int height = 380;
        int x = (screenWidth - width) / 2;
        int y = (screenHeight - height) / 2;
        this.setLocation(x, y);
        this.setTitle("聊天框");
        this.setLayout(null);
        init();
        this.setSize(width, height);
        this.setResizable(false);
        this.setVisible(true);
    }

    public void init() {
        //ip：保存输入的ip地址
        ip = JOptionPane.showInputDialog("请输入连接的IP地址");
        //输入框
        sendField = new JTextField();
        sendField.setBounds(0, 300, 230, 50);
        sendField.setFont(new Font("宋体", Font.BOLD, 25));
        this.add(sendField);
        //发送按钮
        sendButton = new JButton("发送");
        sendButton.setBounds(235, 300, 70, 50);
        this.add(sendButton);
        //存放JTextArea 使有文本有滚轮
        scrollPane = new JScrollPane();
        scrollPane.setBounds(0, 0, 300, 295);
        scrollPane.setHorizontalScrollBarPolicy(JScrollPane.HORIZONTAL_SCROLLBAR_NEVER);
        this.add(scrollPane);
        //用来展示聊天内容（通信内容）
        msgArea = new JTextArea();
        msgArea.setBounds(0, 0, 300, 295);
        msgArea.setFont(new Font("宋体", Font.BOLD, 20));
        msgArea.setEditable(false);
        scrollPane.setViewportView(msgArea);
        //StringBuilder用来存放聊天的内容，本机内容与他机内容
        stringBuilder = new StringBuilder();
        //用来格式化时间
        dateFormat = new SimpleDateFormat("yyyy-mm-dd hh:mm:ss");
        //发送按钮添加监听器 用来执行发送消息的线程
        sendButton.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                String text = sendField.getText();
                //如果发送文本不为空，执行发送
                if (text.length() != 0) {
                    String format = dateFormat.format(new Date());
                    //StringBuilder添加发送时间和换行
                    stringBuilder.append(format);
                    stringBuilder.append("\r\n");
                    //StringBuilder添加本机发送内容和换行
                    stringBuilder.append("本机：" + text);
                    stringBuilder.append("\r\n");
                }
                //设置文本域展示展示聊天内容
                msgArea.setText(stringBuilder.toString());
                //开启发送消息线程
                new SendMsg().start();
            }
        });
        //默认一直开启消息接收线程
        new ReceiveMsg().start();
    }

    /**
     * 消息发送线程类
     */
    class SendMsg extends Thread {
        public SendMsg() {

        }

        @Override
        public void run() {
            this.sendMsg();
        }

        public void sendMsg() {
            DatagramSocket datagramSocket = null;
            try {
                //创建数据
                datagramSocket = new DatagramSocket(8888);
                String text = sendField.getText();
                //如果发送文本不为空 则发送消息
                if (text.length() != 0) {
                    byte[] bytes = text.getBytes();
                    //通过ip创建 inderAddress对象
                    InetAddress inetAddress = InetAddress.getByName(ip);
                    //常见数据报包
                    DatagramPacket datagramPacket = new DatagramPacket(bytes, bytes.length, inetAddress, 8889);
                    //发送数据报包
                    datagramSocket.send(datagramPacket);
                    //像控制台输出内容  用于调试
                    System.out.println("发送的消息为：" + text);
                    //将发送文本制空  为了下次输入
                    sendField.setText("");
                }
            } catch (Exception se) {
                se.printStackTrace();
            } finally {
                if (datagramSocket != null) {
                    datagramSocket.close();
                }
            }
        }
    }

    /**
     * 消息接收线程
     */
    class ReceiveMsg extends Thread {

        public ReceiveMsg() {

        }

        @Override
        public void run() {
            this.receiveMsg();
        }

        public void receiveMsg() {
            DatagramSocket datagramSocket = null;
            try {
                //消息接收端口为8889
                datagramSocket = new DatagramSocket(8889);
                while (true) {
                    byte[] bytes = new byte[1024];
                    //创建接收信息的数据报包
                    DatagramPacket datagramPacket = new DatagramPacket(bytes, bytes.length);
                    //向控制台输出内容  用于调试程序
                    System.out.println("等待接收消息");
                    datagramSocket.receive(datagramPacket);
                    System.out.println("消息接收成功");
                    //打印收到消息的ip地址
                    System.out.println(datagramPacket.getAddress());
                    byte[] data = datagramPacket.getData();
                    System.out.println(new String(data));
                    String format = dateFormat.format(new Date());
                    //StringBuilder添加接收时间和换行
                    stringBuilder.append(format);
                    stringBuilder.append("\r\n");
                    //StringBuilder添加接收的消息和换行
                    stringBuilder.append("他机:" + new String(data));
                    stringBuilder.append("\r\n");
                    //设置文本域展示展示聊天内容
                    msgArea.setText(stringBuilder.toString());
                }
            } catch (IOException e) {
                e.printStackTrace();
            } finally {
                if (datagramSocket != null) {
                    datagramSocket.close();
                }
            }
        }
    }
}