点对点传输

• 根据UDP信息建立TCP 链接
• TCP 链接准备事项

服务端

package server;

import clink.net.qiujuer.clink.utils.ByteUtils;
import constants.UDPConstants;

import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.nio.ByteBuffer;
import java.util.UUID;

class UDPProvider {
    private static Provider PROVIDER_INSTANCE;

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

    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;
        private boolean done = false;
        private DatagramSocket ds = null;
        // 存储消息的Buffer
        final byte[] buffer = new byte[128];

        Provider(String sn, int port) {
            super();
            this.sn = sn.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("UDPProvider 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("UDPProvider response to:" + clientIp + "\tport:" + responsePort + "\tdataLen:" + len);
                    } else {
                        System.out.println("UDPProvider receive cmd nonsupport; cmd:" + cmd + "\tport:" + port);
                    }
                }
            } catch (Exception ignored) {
            } finally {
                close();
            }

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

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

        /**
         * 提供结束
         */
        void exit() {
            done = true;
            close();
        }
    }
}


package server;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintStream;
import java.net.ServerSocket;
import java.net.Socket;

public class TCPServer {
    private final int port;
    private ClientListener mListener;

    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();
        }
    }

    private static 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;
                }
                // 客户端构建异步线程
                ClientHandler clientHandler = new ClientHandler(client);
                // 启动线程
                clientHandler.start();
            } while (!done);

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

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

    /**
     * 客户端消息处理
     */
    private static class ClientHandler extends Thread {
        private Socket socket;
        private boolean flag = true;

        ClientHandler(Socket socket) {
            this.socket = socket;
        }

        @Override
        public void run() {
            super.run();
            System.out.println("新客户端连接：" + socket.getInetAddress() +
                    " P:" + socket.getPort());

            try {
                // 得到打印流，用于数据输出；服务器回送数据使用
                PrintStream socketOutput = new PrintStream(socket.getOutputStream());
                // 得到输入流，用于接收数据
                BufferedReader socketInput = new BufferedReader(new InputStreamReader(
                        socket.getInputStream()));

                do {
                    // 客户端拿到一条数据
                    String str = socketInput.readLine();
                    if ("bye".equalsIgnoreCase(str)) {
                        flag = false;
                        // 回送
                        socketOutput.println("bye");
                    } else {
                        // 打印到屏幕。并回送数据长度
                        System.out.println(str);
                        socketOutput.println("回送：" + str.length());
                    }

                } while (flag);

                socketInput.close();
                socketOutput.close();

            } catch (Exception e) {
                System.out.println("连接异常断开");
            } finally {
                // 连接关闭
                try {
                    socket.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }

            System.out.println("客户端已退出：" + socket.getInetAddress() +
                    " P:" + socket.getPort());

        }
    }
}


package server;

import constants.TCPConstants;

import java.io.IOException;

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

        UDPProvider.start(TCPConstants.PORT_SERVER);

        try {
            //noinspection ResultOfMethodCallIgnored
            System.in.read();
        } catch (IOException e) {
            e.printStackTrace();
        }

        UDPProvider.stop();
        tcpServer.stop();
    }
}

工具类

package constants;

public class TCPConstants {
    // 服务器固化UDP接收端口
    public static int PORT_SERVER = 30401;
}

package constants;

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

package clink.net.qiujuer.clink.utils;

public class ByteUtils {
    /**
     * Does this byte array begin with match array content?
     *
     * @param source Byte array to examine
     * @param match  Byte array to locate in source
     * @return true If the starting bytes are equal
     */
    public static boolean startsWith(byte[] source, byte[] match) {
        return startsWith(source, 0, match);
    }

    /**
     * Does this byte array begin with match array content?
     *
     * @param source Byte array to examine
     * @param offset An offset into the source array
     * @param match  Byte array to locate in source
     * @return true If the starting bytes are equal
     */
    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;
    }

    /**
     * Does the source array equal the match array?
     *
     * @param source Byte array to examine
     * @param match  Byte array to locate in source
     * @return true If the two arrays are equal
     */
    public static boolean equals(byte[] source, byte[] match) {

        if (match.length != source.length) {
            return false;
        }
        return startsWith(source, 0, match);
    }

    /**
     * Copies bytes from the source byte array to the destination array
     *
     * @param source      The source array
     * @param srcBegin    Index of the first source byte to copy
     * @param srcEnd      Index after the last source byte to copy
     * @param destination The destination array
     * @param dstBegin    The starting offset in the destination array
     */
    public static void getBytes(byte[] source, int srcBegin, int srcEnd, byte[] destination,
                                int dstBegin) {
        System.arraycopy(source, srcBegin, destination, dstBegin, srcEnd - srcBegin);
    }

    /**
     * Return a new byte array containing a sub-portion of the source array
     *
     * @param srcBegin The beginning index (inclusive)
     * @param srcEnd   The ending index (exclusive)
     * @return The new, populated byte array
     */
    public static byte[] subbytes(byte[] source, int srcBegin, int srcEnd) {
        byte destination[];

        destination = new byte[srcEnd - srcBegin];
        getBytes(source, srcBegin, srcEnd, destination, 0);

        return destination;
    }

    /**
     * Return a new byte array containing a sub-portion of the source array
     *
     * @param srcBegin The beginning index (inclusive)
     * @return The new, populated byte array
     */
    public static byte[] subbytes(byte[] source, int srcBegin) {
        return subbytes(source, srcBegin, source.length);
    }
}

客户端

package client;

import client.bean.ServerInfo;

import java.io.IOException;

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();
            }
        }
    }
}


package client;

import client.bean.ServerInfo;

import java.io.*;
import java.net.Inet4Address;
import java.net.InetSocketAddress;
import java.net.Socket;

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() + " P:" + socket.getLocalPort());
        System.out.println("服务器信息：" + socket.getInetAddress() + " P:" + socket.getPort());

        try {
            // 发送接收数据
            todo(socket);
        } 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 todo(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);


        // 得到Socket输入流，并转换为BufferedReader
        InputStream inputStream = client.getInputStream();
        BufferedReader socketBufferedReader = new BufferedReader(new InputStreamReader(inputStream));

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


            // 从服务器读取一行
            String echo = socketBufferedReader.readLine();
            if ("bye".equalsIgnoreCase(echo)) {
                flag = false;
            } else {
                System.out.println(echo);
            }
        } while (flag);

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

    }

}

package client;

import client.bean.ServerInfo;
import clink.net.qiujuer.clink.utils.ByteUtils;
import constants.UDPConstants;

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.nio.ByteBuffer;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.TimeUnit;

public class UDPSearcher {
    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(serverPort, ip, sn);
                    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;
        }
    }
}