安卓CRC32校验

话不多说，直接上代码

/**
 * Created by SiKang on 2017/5/17.
 */
public class CustomData {
    public static void main(String args[]) {
        //服务端线程
        new Thread(new Runnable() {
            @Override
            public void run() {
                try {
                    //开启服务端Socket
                    ServerSocket server = new ServerSocket(9000);
                    //等待客户端连接
                    Socket socket = server.accept();
                    InputStream inputStream = socket.getInputStream();
                    //先得到前两个字节 为报文长度
                    byte[] lenBytes = new byte[2];
                    inputStream.read(lenBytes);
                    short length = bytesToShort(lenBytes);
                    System.out.println("length: " + length);

                    //然后得到接下来的四个字节 crc32校验码
                    byte[] crc = new byte[4];
                    inputStream.read(crc);
                    int crc32 = bytesToInt(crc);

                    //得到剩下的字段 ver、cmd、data
                    byte[] bytes = new byte[length - 2 - 4];
                    inputStream.read(bytes);

                                //根据得到的bytes获取新的Crc32校验码 验证数据是否完整（可以在读取bytes时少读一位，看看能不能通过）
                    if (crc32 == getCRC32(bytes)) {
                        System.out.println("Crc32 Right!");
                    }else{
            System.out.println("Crc32 Error!");
                        return;
            }

                    //取出ver cmd
                    int ver = Integer.parseInt(byteToHex(bytes[0]), 16);
                    int cmd = Integer.parseInt(byteToHex(bytes[1]), 16);
                    //看看ver是否是客户端发送0x05
                    if (ver == 0x05) {
                        System.out.println("ver: 0x05");
                    }
                    //cmd是否是客户端发送0xff
                    if (cmd == 0xff) {
                        System.out.println("cmd: 0xff");
                    }

                    //得到剩下的数据字节数，取出data数据
                    int datalen = length - 2 - 4 - 1 - 1;
                    byte[] data = new byte[datalen];
                    int index = 1;
                    for (int i = 0; i < datalen; i++) {
                        data[i] = bytes[++index];
                    }
                    String str = new String(data);
                    System.out.println("data: " + str);
                    inputStream.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }).start();

        //客户端线程
        new Thread(new Runnable() {
            @Override
            public void run() {
                try {
                    //连接服务端
                    Socket socket = new Socket(getIpAddress(), 9000);
                    OutputStream outputStream = socket.getOutputStream();
                    String str = "Hellow World!";
                    byte[] data = str.getBytes();
                    //发送报文
                    pack(outputStream, (byte) 0xff, data, data.length);
                    outputStream.flush();
                    outputStream.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }).start();
    }

    /**
    *封装并发送报文
    *这里报文格式为{报文总长度[2字节]，Crc32校验码[4字节]，ver版本信息[1字节]，cmd指令[1字节]，data数据内容[若干字节]}
    */
    private static void pack(OutputStream out, byte cmd, byte[] data, int len) {
        try {
            //先得到报文总长度，如上介绍的格式 字节数相加
            short totalSize = (short) (2 + 4 + 1 + 1 + len);
            //输出报文长度
            out.write(shortToByte(totalSize), 0, 2);
            //需要校验的字段
            byte[] bytes = new byte[1 + 1 + len];
            int index = 0;
            bytes[index++] = 0x05;//版本号（这里是写死的）
            bytes[index++] = cmd;//cmd指令
            //数据内容
            for (int i = 0; i < len; i++) {
                bytes[index++] = data[i];
            }
            //得到ver、cmd、data的crc32校验码（Crc32算法在最下边，网上找的.....）
            byte[] crc32 = intToBytes(getCRC32(bytes));
            //输出crc校验码
            out.write(crc32, 0, crc32.length);
            //输出ver、cmd、data
            out.write(bytes, 0, bytes.length);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }


    /**
     * 得到本机IP
     */
    private static String getIpAddress() throws UnknownHostException {
        InetAddress address = InetAddress.getLocalHost();

        return address.getHostAddress();
    }

    /**
     * int转byte[]
     */
    public static byte[] intToBytes(int value) {
        byte[] bytes = new byte[4];
        bytes[3] = (byte) (value >> 24);
        bytes[2] = (byte) (value >> 16);
        bytes[1] = (byte) (value >> 8);
        bytes[0] = (byte) (value >> 0);
        return bytes;
    }

    /**
     * short转byte[]
     */
    public static byte[] shortToByte(short value) {
        byte[] bytes = new byte[2];
        bytes[1] = (byte) (value >> 8);
        bytes[0] = (byte) (value >> 0);
        return bytes;
    }

    /**
     * byte转16进制
     */
    public static String byteToHex(byte b) {
        int i = b & 0xFF;
        return Integer.toHexString(i);
    }

    /**
     * byte[]转int
     */
    public static int bytesToInt(byte[] bytes) {
        return (int) ((((bytes[3] & 0xff) << 24)
                | ((bytes[2] & 0xff) << 16)
                | ((bytes[1] & 0xff) << 8) | ((bytes[0] & 0xff) << 0)));
    }

    /**
     * byte[]转short
     */
    public static short bytesToShort(byte[] bytes) {
        return (short) (((bytes[1] << 8) | bytes[0] & 0xff));
    }

    /**
     * 得到CRC32校验码
     */
    public static int getCRC32(byte[] bytes) {
        int[] table = {
                0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419, 0x706af48f, 0xe963a535, 0x9e6495a3,
                0x0edb8832, 0x79dcb8a4, 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07, 0x90bf1d91,
                0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de, 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7,
                0x136c9856, 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9, 0xfa0f3d63, 0x8d080df5,
                0x3b6e20c8, 0x4c69105e, 0xd56041e4, 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
                0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3, 0x45df5c75, 0xdcd60dcf, 0xabd13d59,
                0x26d930ac, 0x51de003a, 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599, 0xb8bda50f,
                0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924, 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d,
                0x76dc4190, 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f, 0x9fbfe4a5, 0xe8b8d433,
                0x7807c9a2, 0x0f00f934, 0x9609a88e, 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
                0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed, 0x1b01a57b, 0x8208f4c1, 0xf50fc457,
                0x65b0d9c6, 0x12b7e950, 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3, 0xfbd44c65,
                0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2, 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb,
                0x4369e96a, 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5, 0xaa0a4c5f, 0xdd0d7cc9,
                0x5005713c, 0x270241aa, 0xbe0b1010, 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
                0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17, 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad,
                0xedb88320, 0x9abfb3b6, 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615, 0x73dc1683,
                0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8, 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1,
                0xf00f9344, 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb, 0x196c3671, 0x6e6b06e7,
                0xfed41b76, 0x89d32be0, 0x10da7a5a, 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
                0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1, 0xa6bc5767, 0x3fb506dd, 0x48b2364b,
                0xd80d2bda, 0xaf0a1b4c, 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef, 0x4669be79,
                0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236, 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f,
                0xc5ba3bbe, 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31, 0x2cd99e8b, 0x5bdeae1d,
                0x9b64c2b0, 0xec63f226, 0x756aa39c, 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
                0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b, 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21,
                0x86d3d2d4, 0xf1d4e242, 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1, 0x18b74777,
                0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c, 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45,
                0xa00ae278, 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7, 0x4969474d, 0x3e6e77db,
                0xaed16a4a, 0xd9d65adc, 0x40df0b66, 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
                0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605, 0xcdd70693, 0x54de5729, 0x23d967bf,
                0xb3667a2e, 0xc4614ab8, 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b, 0x2d02ef8d,
        };
        int crc = 0xffffffff;
        for (byte b : bytes) {
            crc = (crc >>> 8 ^ table[(crc ^ b) & 0xff]);
        }
        crc = crc ^ 0xffffffff;
        return crc;
    }
}