[java]基于UDP的Socket通信Demo

　　java课编程作业：在老师给的demo的基础上实现客户端发送数据到服务器端，服务器端接受客户端后进行数据广播。

　　整体功能类似于聊天室，代码部分不是太难，但是在本机测试的时候出现这样的问题：

　　　　服务端通过将每一个Socket客户端的IP存入Set集合，每次接受到数据后都向当前所有的IP转发。但是本机演示的时候所有开的ChatClient客户端都是同一IP，怎么测试呢？

　　解决办法就是本机测试时候服务端向多个不同的端口转发就好了，这样跑起来的客户端是在不同端口上进行监听的（只是为了实现广播，实际应用下还是通过IP来转发）。

　　客户端代码：

　　

import javax.print.attribute.HashPrintServiceAttributeSet;
import javax.swing.*;

import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.FlowLayout;
import java.awt.Toolkit;
import java.awt.event.*;
import java.io.*;
import java.net.*;
import java.util.*;

public class ChatClient extends JFrame {

    JTextArea contents = new JTextArea();
    JLabel label1 = new JLabel("服务器地址");
    JTextField address = new JTextField();
    JLabel label2 = new JLabel("用户名");
    JTextField username = new JTextField();
    JButton online = new JButton("上线");
    JButton offline = new JButton("下线");
    JTextField input = new JTextField();
    JButton send = new JButton("发送");

    boolean onlineFlag = false;

    public ChatClient() {
        super("Chat Client");

        contents.setEditable(false);
        getContentPane().add(contents);

        JPanel p1 = new JPanel();
        p1.setLayout(new FlowLayout(FlowLayout.LEADING));

        address.setPreferredSize(new Dimension(100, 28));
        username.setPreferredSize(new Dimension(80, 28));
        input.setPreferredSize(new Dimension(180, 28));

        p1.add(label1);
        p1.add(address);
        p1.add(label2);
        p1.add(username);
        p1.add(online);
        p1.add(offline);
        p1.add(input);
        p1.add(send);

        offline.setEnabled(false);
        send.setEnabled(false);

        getContentPane().add(p1, BorderLayout.SOUTH);

        addWindowListener(new WindowAdapter() {
            public void windowClosing(WindowEvent we) {
                onlineFlag = false;
                Map<String, Object> m1 = new HashMap<String, Object>();
                m1.put("time", new Date()); // 上线时间
                m1.put("username", getUsername());
                m1.put("onlineFlag", onlineFlag);

                send(getServerAddress(), 2222, m1);

                System.exit(0);
            }
        });

        ActionListener al = new ActionListener() {
            public void actionPerformed(ActionEvent ae) {
                String server = getServerAddress();
                if (server == null || server.length() == 0) {
                    JOptionPane.showMessageDialog(ChatClient.this, "请输入服务器地址！");
                    return;
                }

                if (ae.getSource() == online) {
                    // 用户点击了上线按钮
                    if (!onlineFlag) {
                        onlineFlag = true;
                        Map<String, Object> m1 = new HashMap<String, Object>();
                        m1.put("time", new Date()); // 上线时间
                        m1.put("username", getUsername());
                        m1.put("onlineFlag", onlineFlag);
                        online.setEnabled(false);
                        offline.setEnabled(true);
                        send.setEnabled(true);
                        address.setEnabled(false);
                        username.setEnabled(false);
                        send(getServerAddress(), 2222, m1);

                    }
                } else {
                    // 用户点击了下线按钮
                    if (onlineFlag) {
                        onlineFlag = false;
                        Map<String, Object> m1 = new HashMap<String, Object>();
                        m1.put("time", new Date()); // 上线时间
                        m1.put("username", getUsername());
                        m1.put("onlineFlag", onlineFlag);
                        online.setEnabled(true);
                        offline.setEnabled(false);
                        send.setEnabled(false);
                        address.setEnabled(true);
                        username.setEnabled(true);
                        send(getServerAddress(), 2222, m1);
                    }
                }
            }
        };

        ActionListener al2 = new ActionListener() {
            public void actionPerformed(ActionEvent ae) {
                Map<String, Object> m1 = new HashMap<String, Object>();
                m1.put("time", new Date());
                m1.put("username", getUsername());
                m1.put("input", getInput());
                send(getServerAddress(), 2222, m1);
            }
        };

        send.addActionListener(al2);

        online.addActionListener(al);
        offline.addActionListener(al);

        // setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setSize(720, 400);
        Dimension d = Toolkit.getDefaultToolkit().getScreenSize();

        setLocation((d.width - 720) / 2, (d.height - 400) / 2);
        setVisible(true);

        new Thread() {
            public void run() {
                try {
                    // 在2221端口接收服务器发送过来的聊天内容，包括上线，下线消息。
                    DatagramSocket rSocket = new DatagramSocket(2220);
                    while (true) {
                        byte[] buffer = new byte[1024 * 16];
                        DatagramPacket recvPacket = new DatagramPacket(buffer, buffer.length);
                        rSocket.receive(recvPacket);
                        byte[] data = recvPacket.getData();
                        byte[] recvData = new byte[recvPacket.getLength()];
                        System.arraycopy(buffer, 0, recvData, 0, recvData.length);
                        //将从服务器接收的数据存入Map并显示
                        Map<String, Object> map = convertByteArrayToMap(recvData);
                        if (map.containsKey("onlineFlag")) { // 上线或者下线
                            boolean b = (boolean) map.get("onlineFlag");
                            if (b) { // 上线
                                map.put("input", "上线");
                            } else { // 下线
                                map.put("input", "下线");
                            }
                        }
                        Date time = (Date) map.get("time");
                        String s = convertDateToFormatString(time);
                        String user = (String) map.get("username");
                        user = "[" + user + "]";
                        contents.append(s + user + ": " + (String) map.get("input") + "\r\n");
                    }
                } catch (Exception e) {
                    e.printStackTrace();
                }

            }
        }.start();

    }

    public String getServerAddress() {
        String s = address.getText();
        //trim删除多余空格
        s = s.trim();
        return s;
    }

    public String getUsername() {
        String s = username.getText();
        s = s.trim();
        if (s == null || s.length() == 0) {
            s = "匿名";
        }
        return s;
    }

    public String getInput() {
        String s = input.getText();
        s = s.trim();
        if (s == null || s.length() == 0) {
            s = "不想说什么";
        }
        return s;
    }

    public static String convertDateToFormatString(Date d) {
        return new java.text.SimpleDateFormat("(yyyy-MM-dd HH:mm:ss)").format(d);
    }

    public static void send(String ip, int port, Map<String, Object> map) {
        try {
            byte[] data = convertMapToByteArray(map);
            DatagramSocket socket = new DatagramSocket();
            DatagramPacket packet = new DatagramPacket(data, data.length);

            packet.setSocketAddress(new InetSocketAddress(ip, port));
            socket.send(packet);

        } catch (Exception e) {
            e.printStackTrace();
        }

    }

    public static byte[] convertMapToByteArray(Map<String, Object> map) {
        try {
            //完成此代码块，要求将map集合中的数据转换成字节数组

            ByteArrayOutputStream b = new ByteArrayOutputStream();
            ObjectOutputStream ois = new ObjectOutputStream(b);
            ois.writeObject(map);
            byte[] temp = b.toByteArray();
            return temp;

        } catch (Exception e) {
            e.printStackTrace();
        }
        return null;
    }

    public static Map<String, Object> convertByteArrayToMap(byte[] data) {
        try {
            ByteArrayInputStream bais = new ByteArrayInputStream(data);
            ObjectInputStream ois = new ObjectInputStream(bais);
            Map<String, Object> result = (Map<String, Object>) ois.readObject();
            return result;
        } catch (Exception e) {
            e.printStackTrace();
        }
        return null;
    }

    public static void main(String[] args) {
        new ChatClient();
    }

}

　　　　服务端代码：

import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetSocketAddress;

import java.util.*;
import java.util.concurrent.LinkedBlockingQueue;

public class ChatServer {

    LinkedBlockingQueue<Map<String, Object>> queue = new LinkedBlockingQueue<Map<String, Object>>();
    Set<String> onlineIPs = new HashSet<String>(); // 当前在线IP。

    public ChatServer() {
        try {

            new Thread() {
                public void run() {
                    while (true) {
                        try {
                            //补齐程序，要求从接收队列中取出数据，遍历在线IP集合，向所有在线IP发送数据

                            if( !queue.isEmpty() ){
                                if( !onlineIPs.isEmpty() ){
                                    for(String ip : onlineIPs){
                                        //下面的端口号可以自定义增加，初始转发至2220端口   多增加的端口可以实现本机内的广播
                                        ChatClient.send(ip, 2221, queue.peek() );
                                        ChatClient.send(ip, 2220, queue.remove() );
                                    }
                                }
                            }

                            //end
                        } catch (Exception e) {
                            e.printStackTrace();
                        }
                    }
                }
            }.start();
            //接受端口2222
            DatagramSocket serverSocket = new DatagramSocket(2222);
            System.out.println("Chat Server started.");
            while (true) {
                byte[] buffer = new byte[1024 * 16];
                DatagramPacket recvPacket = new DatagramPacket(buffer, buffer.length);

                serverSocket.receive(recvPacket);

                InetSocketAddress remoteAddress = new InetSocketAddress(recvPacket.getAddress(),
                        recvPacket.getPort());
                System.out.println("接收到 " + remoteAddress.getHostString() + " 发送过来的数据包");

                byte[] data = recvPacket.getData();
                byte[] recvData = new byte[recvPacket.getLength()];
                System.arraycopy(buffer, 0, recvData, 0, recvData.length);
                System.out.println(recvData.length);
                Map<String, Object> map = ChatClient.convertByteArrayToMap(recvData);
                System.out.print("map长度"+map.size());
                if (map.containsKey("onlineFlag")) { // 上线或者下线
                    boolean b = (boolean) map.get("onlineFlag");
                    if (b) { // 上线
                        onlineIPs.add(remoteAddress.getHostString());
                    } else { // 下线
                        onlineIPs.remove(remoteAddress.getHostString());
                    }
                }

                queue.add(map);

            }

        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public static void main(String[] args) {
        new ChatServer();

    }

}