socket网络编程-UDP辅助TCP实现点对点传输

UDP搜索IP和端口

客户端回送数据到服务器的流程

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服务器回送数据到客户端

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我就直接贴代码了

• UDPConstants

public class UDPConstants {
    //公用头部
    public static byte[] HEADER = new byte[]{7, 7, 7, 7, 7, 7, 7, 7};
    //服务器UDP接受端口
    public static int PORT_SERVER = 30201;
    //客户端回送端口
    public static int PORT_CLIENT_RESPONSE = 30202;
}

• TCPConstants

public class TCPConstants {
    //服务器固定端口
    public static int PORT_SERVER=30401;
}

• ByteUtils

 public static boolean startsWith(byte[] source, byte[] match) {
        return startsWith(source, 0, match);
    }

    public static boolean startsWith(byte[] source, int offset, byte[] match) {

        if (match.length > (source.length - offset)) {
            return false;
        }

        for (int i = 0; i < match.length; i++) {
            if (source[offset + i] != match[i]) {
                return false;
            }
        }
        return true;
    }

上面三个其实很简单，就是定义一些常量和工具类使用

• Server服务器端

public class Server {
    public static void main(String[] args) {
        ServerProvider.start(TCPConstants.PORT_SERVER);
        try {
            System.in.read();
        } catch (IOException e) {
            e.printStackTrace();
        }
        ServerProvider.stop();
    }
}

• ServerProvider:相当于服务器提供类

public class ServerProvider {
    private static Provider PROVIDER_INSTANCE;

    public static void start(int port) {
        stop();
        String uuid = UUID.randomUUID().toString();
        Provider provider = new Provider(uuid, port);
        provider.start();
        PROVIDER_INSTANCE = provider;
    }

    public static void stop() {
        if (PROVIDER_INSTANCE != null) {
            PROVIDER_INSTANCE.exit();
            PROVIDER_INSTANCE = null;
        }
    }

    private static class Provider extends Thread {
        private final byte[] sn;
        private final int port;
        //tcp端口
        private boolean done = false;
        //发送
        private DatagramSocket ds = null;
        //存储消息的buffer
        final byte[] buffer = new byte[128];

        public Provider(String uuid, int port) {
            super();
            this.sn = uuid.getBytes();
            this.port = port;
        }

        @Override
        public void run() {
            super.run();

            System.out.println("UDPProvider Started.");

            try {
                // 监听20000 端口
                ds = new DatagramSocket(UDPConstants.PORT_SERVER);
                // 接收消息的Packet
                DatagramPacket receivePack = new DatagramPacket(buffer, buffer.length);

                while (!done) {

                    // 接收
                    ds.receive(receivePack);

                    // 打印接收到的信息与发送者的信息
                    // 发送者的IP地址
                    String clientIp = receivePack.getAddress().getHostAddress();
                    int clientPort = receivePack.getPort();
                    int clientDataLen = receivePack.getLength();
                    byte[] clientData = receivePack.getData();
                    boolean isValid = clientDataLen >= (UDPConstants.HEADER.length + 2 + 4)
                            && ByteUtils.startsWith(clientData, UDPConstants.HEADER);

                    System.out.println("ServerProvider receive form ip:" + clientIp
                            + "\tport:" + clientPort + "\tdataValid:" + isValid);

                    if (!isValid) {
                        // 无效继续
                        continue;
                    }

                    // 解析命令与回送端口
                    int index = UDPConstants.HEADER.length;
                    short cmd = (short) ((clientData[index++] << 8) | (clientData[index++] & 0xff));
                    int responsePort = (((clientData[index++]) << 24) |
                            ((clientData[index++] & 0xff) << 16) |
                            ((clientData[index++] & 0xff) << 8) |
                            ((clientData[index] & 0xff)));

                    // 判断合法性
                    if (cmd == 1 && responsePort > 0) {
                        // 构建一份回送数据
                        ByteBuffer byteBuffer = ByteBuffer.wrap(buffer);
                        byteBuffer.put(UDPConstants.HEADER);
                        byteBuffer.putShort((short) 2);
                        byteBuffer.putInt(port);
                        byteBuffer.put(sn);
                        int len = byteBuffer.position();
                        // 直接根据发送者构建一份回送信息
                        DatagramPacket responsePacket = new DatagramPacket(buffer,
                                len,
                                receivePack.getAddress(),
                                responsePort);
                        ds.send(responsePacket);
                        System.out.println("ServerProvider response to:" + clientIp + "\tport:" + responsePort + "\tdataLen:" + len);
                    } else {
                        System.out.println("ServerProvider receive cmd nonsupport; cmd:" + cmd + "\tport:" + port);
                    }
                }
            } catch (Exception ignored) {
            } finally {
                close();
            }

            // 完成
            System.out.println("UDPProvider Finished.");
        }

        void exit() {
            done = true;
            close();
        }

        private void close() {
            if (ds != null) {
                ds.close();
                ds = null;
            }
        }
    }
}

如何获取到cmd?

image.png

首先我们结构是头部+cmd+端口+sn，上图显示（只有cmd数据真实，其实虚构，不影响分析）。我们首先左边移动8位，右边补零，则得到上面图片的第二行数据，clientData[index++] << 8)
随后我们获取cmd的二进制(clientData[index++] & 0xff),左边全部补零，最后进行或(|)运算.或运算是有1显示1，没有显示0

• 客户端client

public class Client {
    public static void main(String[] args) {
        ServerInfo info=ClientSearch.searchServer(10000);//10s
        System.out.println("Server:"+info);
    }
}

• ClientSearch

public class ClientSearch {
    private static final int LISTEN_PORT = UDPConstants.PORT_CLIENT_RESPONSE;

    public static ServerInfo searchServer(int timeout) {
        System.out.println("UDPSearcher Started.");

        // 成功收到回送的栅栏
        CountDownLatch receiveLatch = new CountDownLatch(1);
        Listener listener = null;
        try {
            listener = listen(receiveLatch);
            sendBroadcast();
            receiveLatch.await(timeout, TimeUnit.MILLISECONDS);
        } catch (Exception e) {
            e.printStackTrace();
        }
        // 完成
        System.out.println("UDPSearcher Finished.");
        if (listener == null) {
            return null;
        }
        List devices = listener.getServerAndClose();
        if (devices.size() > 0) {
            return devices.get(0);
        }
        return null;
    }

    private static Listener listen(CountDownLatch receiveLatch) throws InterruptedException {
        System.out.println("UDPSearcher start listen.");
        CountDownLatch startDownLatch = new CountDownLatch(1);
        Listener listener = new Listener(LISTEN_PORT, startDownLatch, receiveLatch);
        listener.start();
        startDownLatch.await();
        return listener;
    }

    private static void sendBroadcast() throws IOException {
        System.out.println("UDPSearcher sendBroadcast started.");

        // 作为搜索方，让系统自动分配端口
        DatagramSocket ds = new DatagramSocket();

        // 构建一份请求数据
        ByteBuffer byteBuffer = ByteBuffer.allocate(128);
        // 头部
        byteBuffer.put(UDPConstants.HEADER);
        // CMD命名
        byteBuffer.putShort((short) 1);
        // 回送端口信息
        byteBuffer.putInt(LISTEN_PORT);
        // 直接构建packet
        DatagramPacket requestPacket = new DatagramPacket(byteBuffer.array(),
                byteBuffer.position() + 1);
        // 广播地址
        requestPacket.setAddress(InetAddress.getByName("255.255.255.255"));
        // 设置服务器端口
        requestPacket.setPort(UDPConstants.PORT_SERVER);

        // 发送
        ds.send(requestPacket);
        ds.close();

        // 完成
        System.out.println("UDPSearcher sendBroadcast finished.");
    }

    private static class Listener extends Thread {
        private final int listenPort;
        private final CountDownLatch startDownLatch;
        private final CountDownLatch receiveDownLatch;
        private final List serverInfoList = new ArrayList<>();
        private final byte[] buffer = new byte[128];
        private final int minLen = UDPConstants.HEADER.length + 2 + 4;
        private boolean done = false;
        private DatagramSocket ds = null;

        private Listener(int listenPort, CountDownLatch startDownLatch, CountDownLatch receiveDownLatch) {
            super();
            this.listenPort = listenPort;
            this.startDownLatch = startDownLatch;
            this.receiveDownLatch = receiveDownLatch;
        }

        @Override
        public void run() {
            super.run();

            // 通知已启动
            startDownLatch.countDown();
            try {
                // 监听回送端口
                ds = new DatagramSocket(listenPort);
                // 构建接收实体
                DatagramPacket receivePack = new DatagramPacket(buffer, buffer.length);

                while (!done) {
                    // 接收
                    ds.receive(receivePack);

                    // 打印接收到的信息与发送者的信息
                    // 发送者的IP地址
                    String ip = receivePack.getAddress().getHostAddress();
                    int port = receivePack.getPort();
                    int dataLen = receivePack.getLength();
                    byte[] data = receivePack.getData();
                    boolean isValid = dataLen >= minLen
                            && ByteUtils.startsWith(data, UDPConstants.HEADER);

                    System.out.println("UDPSearcher receive form ip:" + ip
                            + "\tport:" + port + "\tdataValid:" + isValid);

                    if (!isValid) {
                        // 无效继续
                        continue;
                    }

                    ByteBuffer byteBuffer = ByteBuffer.wrap(buffer, UDPConstants.HEADER.length, dataLen);
                    final short cmd = byteBuffer.getShort();
                    final int serverPort = byteBuffer.getInt();
                    if (cmd != 2 || serverPort <= 0) {
                        System.out.println("UDPSearcher receive cmd:" + cmd + "\tserverPort:" + serverPort);
                        continue;
                    }

                    String sn = new String(buffer, minLen, dataLen - minLen);
                    ServerInfo info = new ServerInfo( sn,serverPort, ip);
                    serverInfoList.add(info);
                    // 成功接收到一份
                    receiveDownLatch.countDown();
                }
            } catch (Exception ignored) {
            } finally {
                close();
            }
            System.out.println("UDPSearcher listener finished.");
        }

        private void close() {
            if (ds != null) {
                ds.close();
                ds = null;
            }
        }

        List getServerAndClose() {
            done = true;
            close();
            return serverInfoList;
        }
    }

}

• ServerInfo只是一个实体类的封装

public class ServerInfo {
    private String sn;
    private int port;
    private String address;

    public ServerInfo(String sn, int port, String address) {
        this.sn = sn;
        this.port = port;
        this.address = address;
    }
.....
}

UDP实现点对点传输

首先客户端我们需要获取数据和读取数据，在上面一步，我们其实已经获取到TCP的IP和端口号

public class Client {
    public static void main(String[] args) {
        ServerInfo info = UDPSearcher.searchServer(10000);
        System.out.println("Server:" + info);

        if (info != null) {
            try {
                TCPClient.linkWith(info);
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}

image.png

public class TCPClient {
    public static void linkWith(ServerInfo info) throws IOException {
        Socket socket = new Socket();
        // 超时时间
        socket.setSoTimeout(3000);

        // 连接本地，端口2000；超时时间3000ms
        socket.connect(new InetSocketAddress(Inet4Address.getByName(info.getAddress()), info.getPort()), 3000);

        System.out.println("已发起服务器连接，并进入后续流程～");
        System.out.println("客户端信息：" + socket.getLocalAddress() + " 端口号:" + socket.getLocalPort());
        System.out.println("服务器信息：" + socket.getInetAddress() + " 端口号:" + socket.getPort());

        try {
            ReadHandler readHandler = new ReadHandler(socket.getInputStream());
            readHandler.start();

            // 发送接收数据
            write(socket);

            // 退出操作
            readHandler.exit();
        } catch (Exception e) {
            System.out.println("异常关闭");
        }

        // 释放资源
        socket.close();
        System.out.println("客户端已退出～");
    }

    private static void write(Socket client) throws IOException {
        // 构建键盘输入流
        InputStream in = System.in;
        BufferedReader input = new BufferedReader(new InputStreamReader(in));

        // 得到Socket输出流，并转换为打印流
        OutputStream outputStream = client.getOutputStream();
        PrintStream socketPrintStream = new PrintStream(outputStream);

        do {
            // 键盘读取一行
            String str = input.readLine();
            // 发送到服务器
            socketPrintStream.println(str);

            if ("bye".equalsIgnoreCase(str)) {
                break;
            }
        } while (true);

        // 资源释放
        socketPrintStream.close();
    }

    static class ReadHandler extends Thread {
        private boolean done = false;
        private final InputStream inputStream;

        ReadHandler(InputStream inputStream) {
            this.inputStream = inputStream;
        }

        @Override
        public void run() {
            super.run();
            try {
                // 得到输入流，用于接收数据
                BufferedReader socketInput = new BufferedReader(new InputStreamReader(inputStream));

                do {
                    String str;
                    try {
                        // 客户端拿到一条数据
                        str = socketInput.readLine();
                    } catch (SocketTimeoutException e) {
                        continue;
                    }
                    if (str == null) {
                        System.out.println("连接已关闭，无法读取数据！");
                        break;
                    }
                    // 打印到屏幕
                    System.out.println(str);
                } while (!done);
            } catch (Exception e) {
                if (!done) {
                    System.out.println("连接异常断开：" + e.getMessage());
                }
            } finally {
                // 连接关闭
                try {
                    if(inputStream!=null){
                        inputStream.close();
                    }
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }

        void exit() {
            done = true;
            try {
                if(inputStream!=null){
                    inputStream.close();
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}

• 服务器端:将数据传给封装好的tcp传输给客户端

public class Server {

    public static void main(String[] args) throws IOException {
        //tcp的端口
        TCPServer tcpServer = new TCPServer(TCPConstants.PORT_SERVER);
        boolean isSucceed = tcpServer.start();
        if (!isSucceed) {
            System.out.println("Start TCP server failed!");
            return;
        }

        ServerProvider.start(TCPConstants.PORT_SERVER);

        BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(System.in));
        String str;
        do {
            str = bufferedReader.readLine();
            tcpServer.broadcast(str);
        } while (!"bye".equalsIgnoreCase(str));

        ServerProvider.stop();
        tcpServer.stop();
    }
}

image.png

public class TCPServer {
    private final int port;
    private ClientListener mListener;
    private List clientHandlerList = new ArrayList<>();

    public TCPServer(int port) {
        this.port = port;
    }

    public boolean start() {
        try {
            ClientListener listener = new ClientListener(port);
            mListener = listener;
            listener.start();
        } catch (IOException e) {
            e.printStackTrace();
            return false;
        }
        return true;
    }

    public void stop() {
        if (mListener != null) {
            mListener.exit();
        }

        for (ClientHandler clientHandler : clientHandlerList) {
            clientHandler.exit();
        }

        clientHandlerList.clear();
    }

    public void broadcast(String str) {
        for (ClientHandler clientHandler : clientHandlerList) {
            clientHandler.send(str);
        }
    }

    private class ClientListener extends Thread {
        private ServerSocket server;
        private boolean done = false;

        private ClientListener(int port) throws IOException {
            server = new ServerSocket(port);
            System.out.println("服务器信息：" + server.getInetAddress() + " P:" + server.getLocalPort());
        }

        @Override
        public void run() {
            super.run();

            System.out.println("服务器准备就绪～");
            // 等待客户端连接
            do {
                // 得到客户端
                Socket client;
                try {
                    client = server.accept();
                } catch (IOException e) {
                    continue;
                }
                try {
                    // 客户端构建异步线程
                    ClientHandler clientHandler = new ClientHandler(client,
                            new ClientHandler.CloseNotify() {
                                @Override
                                public void onSelfClosed(ClientHandler handler) {
                                    clientHandlerList.remove(handler);
                                }
                            });
                    // 读取数据并打印
                    clientHandler.readToPrint();
                    clientHandlerList.add(clientHandler);
                } catch (IOException e) {
                    e.printStackTrace();
                    System.out.println("客户端连接异常：" + e.getMessage());
                }
            } while (!done);

            System.out.println("服务器已关闭！");
        }

        void exit() {
            done = true;
            try {
                server.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}

实际真正逻辑在ClientHandler

public class ClientHandler {
    private final Socket socket;
    private final ClientReadHandler readHandler;
    private final ClientWriteHandler writeHandler;
    private final CloseNotify closeNotify;

    public ClientHandler(Socket socket, CloseNotify closeNotify) throws IOException {
        this.socket = socket;
        this.readHandler = new ClientReadHandler(socket.getInputStream());
        this.writeHandler = new ClientWriteHandler(socket.getOutputStream());
        this.closeNotify = closeNotify;
        System.out.println("新客户端连接：" + socket.getInetAddress() +
                " P:" + socket.getPort());
    }

    public void exit() {
        readHandler.exit();
        writeHandler.exit();
        CloseUtils.close(socket);
        System.out.println("客户端已退出：" + socket.getInetAddress() +
                " P:" + socket.getPort());
    }

    public void send(String str) {
        writeHandler.send(str);
    }

    public void readToPrint() {
        readHandler.start();
    }

    private void exitBySelf() {
        exit();
        closeNotify.onSelfClosed(this);
    }

    public interface CloseNotify {
        void onSelfClosed(ClientHandler handler);
    }

    class ClientReadHandler extends Thread {
        private boolean done = false;
        private final InputStream inputStream;

        ClientReadHandler(InputStream inputStream) {
            this.inputStream = inputStream;
        }

        @Override
        public void run() {
            super.run();
            try {
                // 得到输入流，用于接收数据
                BufferedReader socketInput = new BufferedReader(new InputStreamReader(inputStream));

                do {
                    // 客户端拿到一条数据
                    String str = socketInput.readLine();
                    if (str == null) {
                        System.out.println("客户端已无法读取数据！");
                        // 退出当前客户端
                        ClientHandler.this.exitBySelf();
                        break;
                    }
                    // 打印到屏幕
                    System.out.println(str);
                } while (!done);
            } catch (Exception e) {
                if (!done) {
                    System.out.println("连接异常断开");
                    ClientHandler.this.exitBySelf();
                }
            } finally {
                // 连接关闭
                CloseUtils.close(inputStream);
            }
        }

        void exit() {
            done = true;
            CloseUtils.close(inputStream);
        }
    }

    class ClientWriteHandler {
        private boolean done = false;
        private final PrintStream printStream;
        private final ExecutorService executorService;

        ClientWriteHandler(OutputStream outputStream) {
            this.printStream = new PrintStream(outputStream);
            this.executorService = Executors.newSingleThreadExecutor();
        }

        void exit() {
            done = true;
            CloseUtils.close(printStream);
            executorService.shutdownNow();
        }

        void send(String str) {
            executorService.execute(new WriteRunnable(str));
        }

        class WriteRunnable implements Runnable {
            private final String msg;

            WriteRunnable(String msg) {
                this.msg = msg;
            }

            @Override
            public void run() {
                if (ClientWriteHandler.this.done) {
                    return;
                }

                try {
                    ClientWriteHandler.this.printStream.println(msg);
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        }
    }
}

ClientReadHandler和ClientWriteHandler实现 数据的发送和接收数据并行