Need help in correcting issues in CRC-ITU check method written in java

Question

We are trying to code GPS device listener on Java.

While doing this, we are unable to develop the right Code for the CRC-ITU error check. The explanation for the crc code generation from protocol document is as below

A check code may be used by the terminal or the server to distinguish whether the received information is in error or not. To prevent errors occurring during data transmission, error check is added to against data misoperation, so as to increase the security and efficiency of the system. The check code is generated by the CRC-ITU checking method. The check codes of data in the structure of the protocol, from the Packet Length to the Information Serial Number (including “Packet Length” and “Information Serial Number”), are values of CRC-ITU. If a CRC error occurs when the received information is calculated, the receiver will ignore and discard the data packet.

This is the data listener class

      byte[] data = new byte[20];
   System.out.println("Waiting for client on port " + serverSocket.getLocalPort() + "...");
                    Socket server = serverSocket.accept();
                    System.out.println("Just connected to " + server.getRemoteSocketAddress());
                    DataInputStream in = new DataInputStream(server.getInputStream());
                    System.out.println("in = " + in);
                    int packetSize = in.read(data, 0, data.length);
                    StringBuilder sb1 = new StringBuilder();
                    for (byte b : data) {
                        sb1.append(String.format("%02X ", b));
                    }
                    System.out.println("loginpacketHex = " + sb1.toString());
                    for (byte b : data) {
                        System.out.println("loginpacketinbytes = " + b);
                    }
                    NewClass cl = new NewClass();
                    byte[] t = new byte[4];
                    byte[] f = new byte[10];
                    t[0] = 0x05;
                    t[1] = data[3];
                    System.out.println(" t[1] = " + t[1]);
                    t[2] = data[data[2] - 6 + 5];
                    System.out.println("t[2] = " + t[2]);
                    t[3] = data[data[2] - 5 + 5];
                    System.out.println("t[3] = " + t[3]);
                    cl.set(t);
                    short x = cl.get();
                    f[0] = 0x78;
                    f[1] = 0x78;
                    f[2] = 0x05;
                    f[3] = data[3];
                    f[4] = data[data[2] - 6 + 5];
                    f[5] = data[data[2] - 5 + 5];
                    f[6] = (byte) ((x >> 8) & 0xff);
                    f[7] = (byte) (x & 0xff);
                    f[8] = 0x0d;
                    f[9] = 0x0a;

This is Crc generation class

public class NewClass {

    public static int crc;

    public static int[] table = {
        0x0000, 0x1189, 0x2312, 0x329B, 0x4624, 0x57AD, 0x6536, 0x74BF,
        0x8C48, 0x9DC1, 0xAF5A, 0xBED3, 0xCA6C, 0xDBE5, 0xE97E, 0xF8F7,
        0x1081, 0x0108, 0x3393, 0x221A, 0x56A5, 0x472C, 0x75B7, 0x643E,
        0x9CC9, 0x8D40, 0xBFDB, 0xAE52, 0xDAED, 0xCB64, 0xF9FF, 0xE876,
        0x2102, 0x308B, 0x0210, 0x1399, 0x6726, 0x76AF, 0x4434, 0x55BD,
        0xAD4A, 0xBCC3, 0x8E58, 0x9FD1, 0xEB6E, 0xFAE7, 0xC87C, 0xD9F5,
        0x3183, 0x200A, 0x1291, 0x0318, 0x77A7, 0x662E, 0x54B5, 0x453C,
        0xBDCB, 0xAC42, 0x9ED9, 0x8F50, 0xFBEF, 0xEA66, 0xD8FD, 0xC974,
        0x4204, 0x538D, 0x6116, 0x709F, 0x0420, 0x15A9, 0x2732, 0x36BB,
        0xCE4C, 0xDFC5, 0xED5E, 0xFCD7, 0x8868, 0x99E1, 0xAB7A, 0xBAF3,
        0x5285, 0x430C, 0x7197, 0x601E, 0x14A1, 0x0528, 0x37B3, 0x263A,
        0xDECD, 0xCF44, 0xFDDF, 0xEC56, 0x98E9, 0x8960, 0xBBFB, 0xAA72,
        0x6306, 0x728F, 0x4014, 0x519D, 0x2522, 0x34AB, 0x0630, 0x17B9,
        0xEF4E, 0xFEC7, 0xCC5C, 0xDDD5, 0xA96A, 0xB8E3, 0x8A78, 0x9BF1,
        0x7387, 0x620E, 0x5095, 0x411C, 0x35A3, 0x242A, 0x16B1, 0x0738,
        0xFFCF, 0xEE46, 0xDCDD, 0xCD54, 0xB9EB, 0xA862, 0x9AF9, 0x8B70,
        0x8408, 0x9581, 0xA71A, 0xB693, 0xC22C, 0xD3A5, 0xE13E, 0xF0B7,
        0x0840, 0x19C9, 0x2B52, 0x3ADB, 0x4E64, 0x5FED, 0x6D76, 0x7CFF,
        0x9489, 0x8500, 0xB79B, 0xA612, 0xD2AD, 0xC324, 0xF1BF, 0xE036,
        0x18C1, 0x0948, 0x3BD3, 0x2A5A, 0x5EE5, 0x4F6C, 0x7DF7, 0x6C7E,
        0xA50A, 0xB483, 0x8618, 0x9791, 0xE32E, 0xF2A7, 0xC03C, 0xD1B5,
        0x2942, 0x38CB, 0x0A50, 0x1BD9, 0x6F66, 0x7EEF, 0x4C74, 0x5DFD,
        0xB58B, 0xA402, 0x9699, 0x8710, 0xF3AF, 0xE226, 0xD0BD, 0xC134,
        0x39C3, 0x284A, 0x1AD1, 0x0B58, 0x7FE7, 0x6E6E, 0x5CF5, 0x4D7C,
        0xC60C, 0xD785, 0xE51E, 0xF497, 0x8028, 0x91A1, 0xA33A, 0xB2B3,
        0x4A44, 0x5BCD, 0x6956, 0x78DF, 0x0C60, 0x1DE9, 0x2F72, 0x3EFB,
        0xD68D, 0xC704, 0xF59F, 0xE416, 0x90A9, 0x8120, 0xB3BB, 0xA232,
        0x5AC5, 0x4B4C, 0x79D7, 0x685E, 0x1CE1, 0x0D68, 0x3FF3, 0x2E7A,
        0xE70E, 0xF687, 0xC41C, 0xD595, 0xA12A, 0xB0A3, 0x8238, 0x93B1,
        0x6B46, 0x7ACF, 0x4854, 0x59DD, 0x2D62, 0x3CEB, 0x0E70, 0x1FF9,
        0xF78F, 0xE606, 0xD49D, 0xC514, 0xB1AB, 0xA022, 0x92B9, 0x8330,
        0x7BC7, 0x6A4E, 0x58D5, 0x495C, 0x3DE3, 0x2C6A, 0x1EF1, 0x0F78,};

    public short get() {
        short c;
        int y;
        y = ~crc;
        c = (short) y;
        return c;
    }

    public void set(byte[] bytes) {
        crc = 0xffff;
        for (byte b : bytes) {
            crc = (crc >>> 8) ^ table[(crc ^ b) & 0xff];
        }
    }

}

Incoming data string comes in following format

    Example of data packet sent by the terminal 78 78 0D 01 01 23 45 67 89 01 23 45 00 01 8C DD 0D 0A

    Explanation

    Start Bit - 0x78 0x78
    Length - 0x0D
    Protocol - 0x01
    Terminal ID - 0x01 0x23 0x45 0x67 0x89 0x01 0x23 0x45
    Serial No - 0x00 0x01
    Error - 0x8C 0xDD
    Stop Bit - 0x0D 0x0A

I am doing like this Updated Code.

ByteArrayOutputStream bytearrypacket = new ByteArrayOutputStream();
        DataOutputStream responce = new DataOutputStream(bytearrypacket);
        responce.writeByte(0x0D);
        responce.writeByte(1);
        responce.writeByte(0x03);
        responce.writeByte(0x53);
        responce.writeByte(0x49);
        responce.writeByte(0x20);
        responce.writeByte(0x49);
        responce.writeByte(0x00);
        responce.writeByte(0x05);
        responce.writeByte(0x34);
        responce.writeShort(2);
        NewClass cl = new NewClass();
        cl.set(bytearrypacket.toByteArray());
        System.out.println("cl = " + cl.get());
        System.out.println("hexhexhex = " + Integer.toHexString(cl.get()));
        responce.writeShort(cl.get());

        byte[] res = bytearrypacket.toByteArray();
        for (byte b : res) {
            System.out.println("b = " + b);
        }

Almost identical to http://stackoverflow.com/questions/20870604/need-help-in-correcting-issues-in-crc-itu-check-method-written-in-javascript-no See if the algorithm in the javascript version gives you any hints as to doing this in Java. — TechTrip, Sep 17 '14 at 11:41
The CRC calculation works fine. What problem are you encountering? — Mark Adler, Sep 17 '14 at 16:27
The CRC in that packet, `D9 DC`, is correct. Your problem is elsewhere. — Mark Adler, Sep 17 '14 at 19:47
I computed the CRC-16 ITU of `05 01 00 01` and it is `D9DC`. So the packet check value is correct. — Mark Adler, Sep 18 '14 at 04:16
The `get()` method of the horribly named "NewClass" class returns a `short`, which is 16 bits. Therefore it cannot be `ffffd9dc`. It can only be `d9dc`. `ffffd9dc` is what you would get if you assigned the `short` `d9dc` to an `int`. The the sign would be extended (since Java only has signed integers), giving you an `int` with `ffffd9dc`. You can get rid of the sign extension with an `& 0xffff`. Or you could store it in a `short`, as it was provided in the first place. — Mark Adler, Sep 18 '14 at 04:18
Leaving the sign extension in the `int` alone would be fine too, since the bytes would be accessed with `(value >> 8) & 0xff` and `value & 0xff`, as in the code in the question, which also strips the sign extension bits. — Mark Adler, Sep 18 '14 at 04:20
78 78 0D 01 03 53 49 20 49 00 05 34 00 02 21 40 0D 0A this the packet I am receiving from device in this crc is 21 40 — user3920792, Sep 18 '14 at 05:00
For this packet I am getting correct crc like 2140 and after byteArray I am getting 33 64. — user3920792, Sep 18 '14 at 05:29

score 0 · Answer 1 · answered Sep 06 '18 at 19:16

Here is the code to calculate the CRC

public class CRCITUUtil {

private static int[] crcItuTable = {
    0X0000, 0X1189, 0X2312, 0X329B, 0X4624, 0X57AD, 0X6536, 0X74BF,
    0X8C48, 0X9DC1, 0XAF5A, 0XBED3, 0XCA6C, 0XDBE5, 0XE97E, 0XF8F7,
    0X1081, 0X0108, 0X3393, 0X221A, 0X56A5, 0X472C, 0X75B7, 0X643E,
    0X9CC9, 0X8D40, 0XBFDB, 0XAE52, 0XDAED, 0XCB64, 0XF9FF, 0XE876,
    0X2102, 0X308B, 0X0210, 0X1399, 0X6726, 0X76AF, 0X4434, 0X55BD,
    0XAD4A, 0XBCC3, 0X8E58, 0X9FD1, 0XEB6E, 0XFAE7, 0XC87C, 0XD9F5,
    0X3183, 0X200A, 0X1291, 0X0318, 0X77A7, 0X662E, 0X54B5, 0X453C,
    0XBDCB, 0XAC42, 0X9ED9, 0X8F50, 0XFBEF, 0XEA66, 0XD8FD, 0XC974,
    0X4204, 0X538D, 0X6116, 0X709F, 0X0420, 0X15A9, 0X2732, 0X36BB,
    0XCE4C, 0XDFC5, 0XED5E, 0XFCD7, 0X8868, 0X99E1, 0XAB7A, 0XBAF3,
    0X5285, 0X430C, 0X7197, 0X601E, 0X14A1, 0X0528, 0X37B3, 0X263A,
    0XDECD, 0XCF44, 0XFDDF, 0XEC56, 0X98E9, 0X8960, 0XBBFB, 0XAA72,
    0X6306, 0X728F, 0X4014, 0X519D, 0X2522, 0X34AB, 0X0630, 0X17B9,
    0XEF4E, 0XFEC7, 0XCC5C, 0XDDD5, 0XA96A, 0XB8E3, 0X8A78, 0X9BF1,
    0X7387, 0X620E, 0X5095, 0X411C, 0X35A3, 0X242A, 0X16B1, 0X0738,
    0XFFCF, 0XEE46, 0XDCDD, 0XCD54, 0XB9EB, 0XA862, 0X9AF9, 0X8B70,
    0X8408, 0X9581, 0XA71A, 0XB693, 0XC22C, 0XD3A5, 0XE13E, 0XF0B7,
    0X0840, 0X19C9, 0X2B52, 0X3ADB, 0X4E64, 0X5FED, 0X6D76, 0X7CFF,
    0X9489, 0X8500, 0XB79B, 0XA612, 0XD2AD, 0XC324, 0XF1BF, 0XE036,
    0X18C1, 0X0948, 0X3BD3, 0X2A5A, 0X5EE5, 0X4F6C, 0X7DF7, 0X6C7E,
    0XA50A, 0XB483, 0X8618, 0X9791, 0XE32E, 0XF2A7, 0XC03C, 0XD1B5,
    0X2942, 0X38CB, 0X0A50, 0X1BD9, 0X6F66, 0X7EEF, 0X4C74, 0X5DFD,
    0XB58B, 0XA402, 0X9699, 0X8710, 0XF3AF, 0XE226, 0XD0BD, 0XC134,
    0X39C3, 0X284A, 0X1AD1, 0X0B58, 0X7FE7, 0X6E6E, 0X5CF5, 0X4D7C,
    0XC60C, 0XD785, 0XE51E, 0XF497, 0X8028, 0X91A1, 0XA33A, 0XB2B3,
    0X4A44, 0X5BCD, 0X6956, 0X78DF, 0X0C60, 0X1DE9, 0X2F72, 0X3EFB,
    0XD68D, 0XC704, 0XF59F, 0XE416, 0X90A9, 0X8120, 0XB3BB, 0XA232,
    0X5AC5, 0X4B4C, 0X79D7, 0X685E, 0X1CE1, 0X0D68, 0X3FF3, 0X2E7A,
    0XE70E, 0XF687, 0XC41C, 0XD595, 0XA12A, 0XB0A3, 0X8238, 0X93B1,
    0X6B46, 0X7ACF, 0X4854, 0X59DD, 0X2D62, 0X3CEB, 0X0E70, 0X1FF9,
    0XF78F, 0XE606, 0XD49D, 0XC514, 0XB1AB, 0XA022, 0X92B9, 0X8330,
    0X7BC7, 0X6A4E, 0X58D5, 0X495C, 0X3DE3, 0X2C6A, 0X1EF1, 0X0F78,
};

public static byte[] getByteArrayFromInt(int value) {
    byte[] result = new byte[4];
    result[0] = (byte) (value >>> 24);
    result[1] = (byte) (value >>> 16);
    result[2] = (byte) (value >>> 8);
    result[3] = (byte) value;
    return result;
}

public static byte[] getCRCITU(byte[] data) {
    int crc = 0xffff;
    for (byte b : data) {
        crc = (crc >>> 8) ^ crcItuTable[(crc ^ b) & 0xff];
    }
    crc = ~crc;
    return getByteArrayFromInt(crc);
}
public static void main(String[] args) {
    byte[] bytes = CRCITUUtil
            .getCRCITU(new byte[] {0x0D, 0x01, 0x01, 0x23, 0x45, 0x67, (byte) 0x89, 0x01, 0x23, 0x45, 0x00, 0x01});
    System.out.println("CRCUIT:"+ Integer.toHexString(0xff & bytes[2]) + " " +  Integer.toHexString(0xff & bytes[3]));
}

}

This will print

CRCUIT:8c dd

Need help in correcting issues in CRC-ITU check method written in java

1 Answers1