socket--TCP和UDP(笔记)

电玩女神 2023-07-12 14:13 45阅读 0赞

## UDP ##

**什么是UDP**

*  一种用户数据协议,又称用户数据报文协议
 *  是一个简单的面向数据报的传输层协议,正式规范为TFC 768
 *  用户数据协议、非连接协议

**不可靠**

*  它一旦把到数据应的数据发送出去，就不保留数据备份。
 *  UDP在IP数据报的头部仅仅加入了复用的数据校验
 *  结构简单、无校验、速度快、容易丢包、可广播
 *  ![2020030821294391.png][]
 *  16位->2字节存储长度信息 共65535
 *  自身占用8字节，数据传入最大长度 65507，超出最好做分包

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM1NDE4NTE4_size_16_color_FFFFFF_t_70][]

**案例**

public class MessageCreator {
        private static final String SN_HEADER = "收到暗号，我是（SN）:";
        private static final String PORT_HEADER = "这是暗号，请回电端口（Port）:";
    
        public static String buildWithPort(int port) {
            return PORT_HEADER + port;
        }
    
        public static int parsePort(String data) {
            if (data.startsWith(PORT_HEADER)) {
                return Integer.parseInt(data.substring(PORT_HEADER.length()));
            }
            return -1;
        }
    
        public static String buildWithSn(String sn) {
            return SN_HEADER + sn;
        }
    
        public static String parseSn(String data) {
            if (data.startsWith(SN_HEADER)) {
                return data.substring(SN_HEADER.length());
            }
            return null;
        }
    }

provider

public class UDPProvider {
    
        public static void main(String[] args) throws IOException {
            // 生成一份唯一标示
            String sn = UUID.randomUUID().toString();
            Provider provider = new Provider(sn);
            provider.start();
    
            // 读取任意键盘信息后可以退出
            //noinspection ResultOfMethodCallIgnored
            System.in.read();
            provider.exit();
        }
    
        private static class Provider extends Thread {
            private final String sn;
            private boolean done = false;
            private DatagramSocket ds = null;
    
            public Provider(String sn) {
                super();
                this.sn = sn;
            }
    
            @Override
            public void run() {
                super.run();
                System.out.println("UDPProvider Started.");
    
                try {
                    // 监听20000 端口
                    ds = new DatagramSocket(20000);
                    while (!done) {
                        // 构建接收实体
                        final byte[] buf = new byte[512];
                        DatagramPacket receivePack = new DatagramPacket(buf, buf.length);
    
                        // 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();
                        String data = new String(receivePack.getData(), 0, dataLen);
                        System.out.println("UDPProvider receive form ip:" + ip
                                + "\tport:" + port + "\tdata:" + data);
    
                        // 解析端口号
                        int responsePort = MessageCreator.parsePort(data);
                        if (responsePort != -1) {
                            // 构建一份回送数据
                            String responseData = MessageCreator.buildWithSn(sn);
                            byte[] responseDataBytes = responseData.getBytes();
                            // 直接根据发送者构建一份回送信息
                            DatagramPacket responsePacket = new DatagramPacket(responseDataBytes,
                                    responseDataBytes.length,
                                    receivePack.getAddress(),
                                    responsePort);
                            ds.send(responsePacket);
                        }
                    }
                } 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();
            }
        }
    }

Searcher

public class UDPSearcher {
        private static final int LISTEN_PORT = 30000;
    
        public static void main(String[] args) throws IOException, InterruptedException {
            System.out.println("UDPSearcher Started.");
            Listener listener = listen();
            sendBroadcast();
    
            // 读取任意键盘信息后可以退出
            //noinspection ResultOfMethodCallIgnored
            System.in.read();
    
            List<Device> devices = listener.getDevicesAndClose();
    
            for (Device device : devices) {
                System.out.println("Device:" + device.toString());
            }
    
            // 完成
            System.out.println("UDPSearcher Finished.");
        }
    
        private static Listener listen() throws InterruptedException {
            System.out.println("UDPSearcher start listen.");
            CountDownLatch countDownLatch = new CountDownLatch(1);
            Listener listener = new Listener(LISTEN_PORT, countDownLatch);
            listener.start();
    
            countDownLatch.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
            String requestData = MessageCreator.buildWithPort(LISTEN_PORT);
            byte[] requestDataBytes = requestData.getBytes();
            // 直接构建packet
            DatagramPacket requestPacket = new DatagramPacket(requestDataBytes,
                    requestDataBytes.length);
            // 20000端口, 广播地址
            requestPacket.setAddress(InetAddress.getByName("255.255.255.255"));
            requestPacket.setPort(20000);
    
            // 发送
            ds.send(requestPacket);
            ds.close();
            // 完成
            System.out.println("UDPSearcher sendBroadcast finished.");
        }
    
        private static class Device {
            final int port;
            final String ip;
            final String sn;
    
            private Device(int port, String ip, String sn) {
                this.port = port;
                this.ip = ip;
                this.sn = sn;
            }
            @Override
            public String toString() {
                return "Device{" +
                        "port=" + port +
                        ", ip='" + ip + '\'' +
                        ", sn='" + sn + '\'' +
                        '}';
            }
        }
    
        private static class Listener extends Thread {
            private final int listenPort;
            private final CountDownLatch countDownLatch;
            private final List<Device> devices = new ArrayList<>();
            private boolean done = false;
            private DatagramSocket ds = null;
            
            public Listener(int listenPort, CountDownLatch countDownLatch) {
                super();
                this.listenPort = listenPort;
                this.countDownLatch = countDownLatch;
            }
            @Override
            public void run() {
                super.run();
    
                // 通知已启动
                countDownLatch.countDown();
                try {
                    // 监听回送端口
                    ds = new DatagramSocket(listenPort);
    
                    while (!done) {
                        // 构建接收实体
                        final byte[] buf = new byte[512];
                        DatagramPacket receivePack = new DatagramPacket(buf, buf.length);
    
                        // 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();
                        String data = new String(receivePack.getData(), 0, dataLen);
                        System.out.println("UDPSearcher receive form ip:" + ip
                                + "\tport:" + port + "\tdata:" + data);
                        String sn = MessageCreator.parseSn(data);
                        if (sn != null) {
                            Device device = new Device(port, ip, sn);
                            devices.add(device);
                        }
                    }
                } catch (Exception ignored) {
    
                } finally {
                    close();
                }
                System.out.println("UDPSearcher listener finished.");
            }
    
            private void close() {
                if (ds != null) {
                    ds.close();
                    ds = null;
                }
            }
    
            List<Device> getDevicesAndClose() {
                done = true;
                close();
                return devices;
            }
        }
    }

## TCP ##

*  几乎UDP能做的都能做，但需要考虑复杂性、性能问题。
 *  具有校验机制（三次握手，四次挥手）、可靠、数据传输稳定
 *  限制：无法进行广播，多播等操作

**三次握手****（连接上）**

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM1NDE4NTE4_size_16_color_FFFFFF_t_70 1][]

*  客户端发起连接 带上一个随机数 x
 *  服务端返回消息，允许连接。并返回 x +1 和一个 随即数 y
 *  客户端依据x找到需要连接的消息，发起连接，并带上需要传递的数据和新的x，y

**四次挥手**（断开连接）

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM1NDE4NTE4_size_16_color_FFFFFF_t_70 2][]

*  客户端发起断开连接信息。
 *  服务端返回收到消息。
 *  服务端继续发送，必要的数据。发送完毕后，回复客户端,可以开始断开连接
 *  客户端返回开始断开连接。

**可靠性**

*  排序、顺序发送、顺序组装：发消息过多时，会分成很多小段。在接收消息时会安装原来的消息顺序，重新排队接收。
 *  丢弃、超时： 发消息过多时，会分成很多小段。其中某一小段丢失，服务端会丢弃数据，然后让客户端重新发送。
 *  重发机制-定时器： 发送许多段数据，网络断开连接。会定时重连，然后重新发送数据。

**案例**

public class Tools {
        public static int byteArrayToInt(byte[] b) {
            return b[3] & 0xFF |
                    (b[2] & 0xFF) << 8 |
                    (b[1] & 0xFF) << 16 |
                    (b[0] & 0xFF) << 24;
        }
    
        public static byte[] intToByteArray(int a) {
            return new byte[]{
                    (byte) ((a >> 24) & 0xFF),
                    (byte) ((a >> 16) & 0xFF),
                    (byte) ((a >> 8) & 0xFF),
                    (byte) (a & 0xFF)
            };
        }
    }

public class Server {
        private static final int PORT = 20000;
    
        public static void main(String[] args) throws IOException {
            ServerSocket server = createServerSocket();
    
            initServerSocket(server);
    
            // 绑定到本地端口上
            server.bind(new InetSocketAddress(Inet4Address.getLocalHost(), PORT), 50);
    
    
            System.out.println("服务器准备就绪～");
            System.out.println("服务器信息：" + server.getInetAddress() + " P:" + server.getLocalPort());
    
    
            // 等待客户端连接
            for (; ; ) {
                // 得到客户端
                Socket client = server.accept();
                // 客户端构建异步线程
                ClientHandler clientHandler = new ClientHandler(client);
                // 启动线程
                clientHandler.start();
            }
    
        }
    
        private static ServerSocket createServerSocket() throws IOException {
            // 创建基础的ServerSocket
            ServerSocket serverSocket = new ServerSocket();
    
            // 绑定到本地端口20000上，并且设置当前可允许等待链接的队列为50个
            //serverSocket = new ServerSocket(PORT);
    
            // 等效于上面的方案，队列设置为50个
            //serverSocket = new ServerSocket(PORT, 50);
    
            // 与上面等同
            // serverSocket = new ServerSocket(PORT, 50, Inet4Address.getLocalHost());
    
            return serverSocket;
        }
    
        private static void initServerSocket(ServerSocket serverSocket) throws IOException {
            // 是否复用未完全关闭的地址端口
            serverSocket.setReuseAddress(true);
    
            // 等效Socket#setReceiveBufferSize
            serverSocket.setReceiveBufferSize(64 * 1024 * 1024);
    
            // 设置serverSocket#accept超时时间
            // serverSocket.setSoTimeout(2000);
    
            // 设置性能参数：短链接，延迟，带宽的相对重要性
            serverSocket.setPerformancePreferences(1, 1, 1);
        }
    
        /**
         * 客户端消息处理
         */
        private static class ClientHandler extends Thread {
            private Socket socket;
    
            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 {
                    // 得到套接字流
                    OutputStream outputStream = socket.getOutputStream();
                    InputStream inputStream = socket.getInputStream();
    
                    byte[] buffer = new byte[256];
                    int readCount = inputStream.read(buffer);
                    ByteBuffer byteBuffer = ByteBuffer.wrap(buffer, 0, readCount);
    
                    // byte
                    byte be = byteBuffer.get();
    
                    // char
                    char c = byteBuffer.getChar();
    
                    // int
                    int i = byteBuffer.getInt();
    
                    // bool
                    boolean b = byteBuffer.get() == 1;
    
                    // Long
                    long l = byteBuffer.getLong();
    
                    // float
                    float f = byteBuffer.getFloat();
    
                    // double
                    double d = byteBuffer.getDouble();
    
                    // String
                    int pos = byteBuffer.position();
                    String str = new String(buffer, pos, readCount - pos - 1);
    
                    System.out.println("收到数量：" + readCount + " 数据："
                            + be + "\n"
                            + c + "\n"
                            + i + "\n"
                            + b + "\n"
                            + l + "\n"
                            + f + "\n"
                            + d + "\n"
                            + str + "\n");
    
                    outputStream.write(buffer, 0, readCount);
                    outputStream.close();
                    inputStream.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());
            }
        }
    }

public class Client {
        private static final int PORT = 20000;
        private static final int LOCAL_PORT = 20001;
    
        public static void main(String[] args) throws IOException {
            Socket socket = createSocket();
    
            initSocket(socket);
    
            // 链接到本地20000端口，超时时间3秒，超过则抛出超时异常
            socket.connect(new InetSocketAddress(Inet4Address.getLocalHost(), PORT), 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 Socket createSocket() throws IOException {
            /*
            // 无代理模式，等效于空构造函数
            Socket socket = new Socket(Proxy.NO_PROXY);
    
            // 新建一份具有HTTP代理的套接字，传输数据将通过www.baidu.com:8080端口转发
            Proxy proxy = new Proxy(Proxy.Type.HTTP,
                    new InetSocketAddress(Inet4Address.getByName("www.baidu.com"), 8800));
            socket = new Socket(proxy);
    
            // 新建一个套接字，并且直接链接到本地20000的服务器上
            socket = new Socket("localhost", PORT);
    
            // 新建一个套接字，并且直接链接到本地20000的服务器上
            socket = new Socket(Inet4Address.getLocalHost(), PORT);
    
            // 新建一个套接字，并且直接链接到本地20000的服务器上，并且绑定到本地20001端口上
            socket = new Socket("localhost", PORT, Inet4Address.getLocalHost(), LOCAL_PORT);
            socket = new Socket(Inet4Address.getLocalHost(), PORT, Inet4Address.getLocalHost(), LOCAL_PORT);
            */
    
            Socket socket = new Socket();
            // 绑定到本地20001端口
            socket.bind(new InetSocketAddress(Inet4Address.getLocalHost(), LOCAL_PORT));
    
            return socket;
        }
    
        private static void initSocket(Socket socket) throws SocketException {
            // 设置读取超时时间为2秒
            socket.setSoTimeout(2000);
    
            // 是否复用未完全关闭的Socket地址，对于指定bind操作后的套接字有效
            socket.setReuseAddress(true);
    
            // 是否开启Nagle算法
            socket.setTcpNoDelay(true);
    
            // 是否需要在长时无数据响应时发送确认数据（类似心跳包），时间大约为2小时
            socket.setKeepAlive(true);
    
            // 对于close关闭操作行为进行怎样的处理；默认为false，0
            // false、0：默认情况，关闭时立即返回，底层系统接管输出流，将缓冲区内的数据发送完成
            // true、0：关闭时立即返回，缓冲区数据抛弃，直接发送RST结束命令到对方，并无需经过2MSL等待
            // true、200：关闭时最长阻塞200毫秒，随后按第二情况处理
            socket.setSoLinger(true, 20);
    
            // 是否让紧急数据内敛，默认false；紧急数据通过 socket.sendUrgentData(1);发送
            socket.setOOBInline(true);
    
            // 设置接收发送缓冲器大小
            socket.setReceiveBufferSize(64 * 1024 * 1024);
            socket.setSendBufferSize(64 * 1024 * 1024);
    
            // 设置性能参数：短链接，延迟，带宽的相对重要性
            socket.setPerformancePreferences(1, 1, 0);
        }
    
        private static void todo(Socket client) throws IOException {
            // 得到Socket输出流
            OutputStream outputStream = client.getOutputStream();
    
    
            // 得到Socket输入流
            InputStream inputStream = client.getInputStream();
            byte[] buffer = new byte[256];
            ByteBuffer byteBuffer = ByteBuffer.wrap(buffer);
    
            // byte
            byteBuffer.put((byte) 126);
    
            // char
            char c = 'a';
            byteBuffer.putChar(c);
    
            // int
            int i = 2323123;
            byteBuffer.putInt(i);
    
            // bool
            boolean b = true;
            byteBuffer.put(b ? (byte) 1 : (byte) 0);
    
            // Long
            long l = 298789739;
            byteBuffer.putLong(l);
    
    
            // float
            float f = 12.345f;
            byteBuffer.putFloat(f);
    
    
            // double
            double d = 13.31241248782973;
            byteBuffer.putDouble(d);
    
            // String
            String str = "Hello你好！";
            byteBuffer.put(str.getBytes());
    
            // 发送到服务器
            outputStream.write(buffer, 0, byteBuffer.position() + 1);
    
            // 接收服务器返回
            int read = inputStream.read(buffer);
            System.out.println("收到数量：" + read);
    
            // 资源释放
            outputStream.close();
            inputStream.close();
        }
    }

[2020030821294391.png]: https://img-blog.csdnimg.cn/2020030821294391.png
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