Reimplement CRC8 and CRC16 calculation

2 files changed, 89 insertions, 178 deletions

diff --git a/src/org/traccar/helper/Checksum.java b/src/org/traccar/helper/Checksum.java
index c4141e7d2..5aed84bf8 100644
--- a/src/org/traccar/helper/Checksum.java
+++ b/src/org/traccar/helper/Checksum.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2012 - 2015 Anton Tananaev (anton@traccar.org)
+ * Copyright 2012 - 2018 Anton Tananaev (anton@traccar.org)
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -24,198 +24,109 @@ public final class Checksum {
     private Checksum() {
     }
 
-    private static final int[] CRC16_CCITT_TABLE_REVERSE = {
-        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
-    };
-
-    private static final int[] CRC16_CCITT_TABLE = {
-        0x0000, 0x1021, 0x2042, 0x3063, 0x4084, 0x50A5, 0x60C6, 0x70E7,
-        0x8108, 0x9129, 0xA14A, 0xB16B, 0xC18C, 0xD1AD, 0xE1CE, 0xF1EF,
-        0x1231, 0x0210, 0x3273, 0x2252, 0x52B5, 0x4294, 0x72F7, 0x62D6,
-        0x9339, 0x8318, 0xB37B, 0xA35A, 0xD3BD, 0xC39C, 0xF3FF, 0xE3DE,
-        0x2462, 0x3443, 0x0420, 0x1401, 0x64E6, 0x74C7, 0x44A4, 0x5485,
-        0xA56A, 0xB54B, 0x8528, 0x9509, 0xE5EE, 0xF5CF, 0xC5AC, 0xD58D,
-        0x3653, 0x2672, 0x1611, 0x0630, 0x76D7, 0x66F6, 0x5695, 0x46B4,
-        0xB75B, 0xA77A, 0x9719, 0x8738, 0xF7DF, 0xE7FE, 0xD79D, 0xC7BC,
-        0x48C4, 0x58E5, 0x6886, 0x78A7, 0x0840, 0x1861, 0x2802, 0x3823,
-        0xC9CC, 0xD9ED, 0xE98E, 0xF9AF, 0x8948, 0x9969, 0xA90A, 0xB92B,
-        0x5AF5, 0x4AD4, 0x7AB7, 0x6A96, 0x1A71, 0x0A50, 0x3A33, 0x2A12,
-        0xDBFD, 0xCBDC, 0xFBBF, 0xEB9E, 0x9B79, 0x8B58, 0xBB3B, 0xAB1A,
-        0x6CA6, 0x7C87, 0x4CE4, 0x5CC5, 0x2C22, 0x3C03, 0x0C60, 0x1C41,
-        0xEDAE, 0xFD8F, 0xCDEC, 0xDDCD, 0xAD2A, 0xBD0B, 0x8D68, 0x9D49,
-        0x7E97, 0x6EB6, 0x5ED5, 0x4EF4, 0x3E13, 0x2E32, 0x1E51, 0x0E70,
-        0xFF9F, 0xEFBE, 0xDFDD, 0xCFFC, 0xBF1B, 0xAF3A, 0x9F59, 0x8F78,
-        0x9188, 0x81A9, 0xB1CA, 0xA1EB, 0xD10C, 0xC12D, 0xF14E, 0xE16F,
-        0x1080, 0x00A1, 0x30C2, 0x20E3, 0x5004, 0x4025, 0x7046, 0x6067,
-        0x83B9, 0x9398, 0xA3FB, 0xB3DA, 0xC33D, 0xD31C, 0xE37F, 0xF35E,
-        0x02B1, 0x1290, 0x22F3, 0x32D2, 0x4235, 0x5214, 0x6277, 0x7256,
-        0xB5EA, 0xA5CB, 0x95A8, 0x8589, 0xF56E, 0xE54F, 0xD52C, 0xC50D,
-        0x34E2, 0x24C3, 0x14A0, 0x0481, 0x7466, 0x6447, 0x5424, 0x4405,
-        0xA7DB, 0xB7FA, 0x8799, 0x97B8, 0xE75F, 0xF77E, 0xC71D, 0xD73C,
-        0x26D3, 0x36F2, 0x0691, 0x16B0, 0x6657, 0x7676, 0x4615, 0x5634,
-        0xD94C, 0xC96D, 0xF90E, 0xE92F, 0x99C8, 0x89E9, 0xB98A, 0xA9AB,
-        0x5844, 0x4865, 0x7806, 0x6827, 0x18C0, 0x08E1, 0x3882, 0x28A3,
-        0xCB7D, 0xDB5C, 0xEB3F, 0xFB1E, 0x8BF9, 0x9BD8, 0xABBB, 0xBB9A,
-        0x4A75, 0x5A54, 0x6A37, 0x7A16, 0x0AF1, 0x1AD0, 0x2AB3, 0x3A92,
-        0xFD2E, 0xED0F, 0xDD6C, 0xCD4D, 0xBDAA, 0xAD8B, 0x9DE8, 0x8DC9,
-        0x7C26, 0x6C07, 0x5C64, 0x4C45, 0x3CA2, 0x2C83, 0x1CE0, 0x0CC1,
-        0xEF1F, 0xFF3E, 0xCF5D, 0xDF7C, 0xAF9B, 0xBFBA, 0x8FD9, 0x9FF8,
-        0x6E17, 0x7E36, 0x4E55, 0x5E74, 0x2E93, 0x3EB2, 0x0ED1, 0x1EF0
-    };
+    public static class Algorithm {
+
+        private int poly;
+        private int init;
+        private boolean refIn;
+        private boolean refOut;
+        private int xorOut;
+        private int[] table;
+
+        public Algorithm(int bits, int poly, int init, boolean refIn, boolean refOut, int xorOut) {
+            this.poly = poly;
+            this.init = init;
+            this.refIn = refIn;
+            this.refOut = refOut;
+            this.xorOut = xorOut;
+            this.table = bits == 8 ? initTable8() : initTable16();
+        }
 
-    private static final int[] CRC16_IBM_TABLE = {
-        0x0000, 0xc0c1, 0xc181, 0x0140, 0xc301, 0x03c0, 0x0280, 0xc241,
-        0xc601, 0x06c0, 0x0780, 0xc741, 0x0500, 0xc5c1, 0xc481, 0x0440,
-        0xcc01, 0x0cc0, 0x0d80, 0xcd41, 0x0f00, 0xcfc1, 0xce81, 0x0e40,
-        0x0a00, 0xcac1, 0xcb81, 0x0b40, 0xc901, 0x09c0, 0x0880, 0xc841,
-        0xd801, 0x18c0, 0x1980, 0xd941, 0x1b00, 0xdbc1, 0xda81, 0x1a40,
-        0x1e00, 0xdec1, 0xdf81, 0x1f40, 0xdd01, 0x1dc0, 0x1c80, 0xdc41,
-        0x1400, 0xd4c1, 0xd581, 0x1540, 0xd701, 0x17c0, 0x1680, 0xd641,
-        0xd201, 0x12c0, 0x1380, 0xd341, 0x1100, 0xd1c1, 0xd081, 0x1040,
-        0xf001, 0x30c0, 0x3180, 0xf141, 0x3300, 0xf3c1, 0xf281, 0x3240,
-        0x3600, 0xf6c1, 0xf781, 0x3740, 0xf501, 0x35c0, 0x3480, 0xf441,
-        0x3c00, 0xfcc1, 0xfd81, 0x3d40, 0xff01, 0x3fc0, 0x3e80, 0xfe41,
-        0xfa01, 0x3ac0, 0x3b80, 0xfb41, 0x3900, 0xf9c1, 0xf881, 0x3840,
-        0x2800, 0xe8c1, 0xe981, 0x2940, 0xeb01, 0x2bc0, 0x2a80, 0xea41,
-        0xee01, 0x2ec0, 0x2f80, 0xef41, 0x2d00, 0xedc1, 0xec81, 0x2c40,
-        0xe401, 0x24c0, 0x2580, 0xe541, 0x2700, 0xe7c1, 0xe681, 0x2640,
-        0x2200, 0xe2c1, 0xe381, 0x2340, 0xe101, 0x21c0, 0x2080, 0xe041,
-        0xa001, 0x60c0, 0x6180, 0xa141, 0x6300, 0xa3c1, 0xa281, 0x6240,
-        0x6600, 0xa6c1, 0xa781, 0x6740, 0xa501, 0x65c0, 0x6480, 0xa441,
-        0x6c00, 0xacc1, 0xad81, 0x6d40, 0xaf01, 0x6fc0, 0x6e80, 0xae41,
-        0xaa01, 0x6ac0, 0x6b80, 0xab41, 0x6900, 0xa9c1, 0xa881, 0x6840,
-        0x7800, 0xb8c1, 0xb981, 0x7940, 0xbb01, 0x7bc0, 0x7a80, 0xba41,
-        0xbe01, 0x7ec0, 0x7f80, 0xbf41, 0x7d00, 0xbdc1, 0xbc81, 0x7c40,
-        0xb401, 0x74c0, 0x7580, 0xb541, 0x7700, 0xb7c1, 0xb681, 0x7640,
-        0x7200, 0xb2c1, 0xb381, 0x7340, 0xb101, 0x71c0, 0x7080, 0xb041,
-        0x5000, 0x90c1, 0x9181, 0x5140, 0x9301, 0x53c0, 0x5280, 0x9241,
-        0x9601, 0x56c0, 0x5780, 0x9741, 0x5500, 0x95c1, 0x9481, 0x5440,
-        0x9c01, 0x5cc0, 0x5d80, 0x9d41, 0x5f00, 0x9fc1, 0x9e81, 0x5e40,
-        0x5a00, 0x9ac1, 0x9b81, 0x5b40, 0x9901, 0x59c0, 0x5880, 0x9841,
-        0x8801, 0x48c0, 0x4980, 0x8941, 0x4b00, 0x8bc1, 0x8a81, 0x4a40,
-        0x4e00, 0x8ec1, 0x8f81, 0x4f40, 0x8d01, 0x4dc0, 0x4c80, 0x8c41,
-        0x4400, 0x84c1, 0x8581, 0x4540, 0x8701, 0x47c0, 0x4680, 0x8641,
-        0x8201, 0x42c0, 0x4380, 0x8341, 0x4100, 0x81c1, 0x8081, 0x4040,
-    };
+        private int[] initTable8() {
+            int[] table = new int[256];
+            int crc;
+            for (int i = 0; i < 256; i++) {
+                crc = i;
+                for (int j = 0; j < 8; j++) {
+                    boolean bit = (crc & 0x80) != 0;
+                    crc <<= 1;
+                    if (bit) {
+                        crc ^= poly;
+                    }
+                }
+                table[i] = crc & 0xFF;
+            }
+            return table;
+        }
 
-    private static final int[] CRC8_TABLE = {
-            0x00, 0x31, 0x62, 0x53, 0xC4, 0xF5, 0xA6, 0x97,
-            0xB9, 0x88, 0xDB, 0xEA, 0x7D, 0x4C, 0x1F, 0x2E,
-            0x43, 0x72, 0x21, 0x10, 0x87, 0xB6, 0xE5, 0xD4,
-            0xFA, 0xCB, 0x98, 0xA9, 0x3E, 0x0F, 0x5C, 0x6D,
-            0x86, 0xB7, 0xE4, 0xD5, 0x42, 0x73, 0x20, 0x11, 0x3F,
-            0x0E, 0x5D, 0x6C, 0xFB, 0xCA, 0x99, 0xA8, 0xC5, 0xF4, 0xA7, 0x96,
-            0x01, 0x30, 0x63, 0x52, 0x7C, 0x4D, 0x1E, 0x2F, 0xB8, 0x89, 0xDA,
-            0xEB, 0x3D, 0x0C, 0x5F, 0x6E, 0xF9, 0xC8, 0x9B, 0xAA, 0x84, 0xB5,
-            0xE6, 0xD7, 0x40, 0x71, 0x22, 0x13, 0x7E, 0x4F, 0x1C, 0x2D, 0xBA,
-            0x8B, 0xD8, 0xE9, 0xC7, 0xF6, 0xA5, 0x94, 0x03, 0x32, 0x61, 0x50,
-            0xBB, 0x8A, 0xD9, 0xE8, 0x7F, 0x4E, 0x1D, 0x2C, 0x02, 0x33, 0x60,
-            0x51, 0xC6, 0xF7, 0xA4, 0x95, 0xF8, 0xC9, 0x9A, 0xAB, 0x3C, 0x0D,
-            0x5E, 0x6F, 0x41, 0x70, 0x23, 0x12, 0x85, 0xB4, 0xE7, 0xD6, 0x7A,
-            0x4B, 0x18, 0x29, 0xBE, 0x8F, 0xDC, 0xED, 0xC3, 0xF2, 0xA1, 0x90,
-            0x07, 0x36, 0x65, 0x54, 0x39, 0x08, 0x5B, 0x6A, 0xFD, 0xCC, 0x9F,
-            0xAE, 0x80, 0xB1, 0xE2, 0xD3, 0x44, 0x75, 0x26, 0x17, 0xFC, 0xCD,
-            0x9E, 0xAF, 0x38, 0x09, 0x5A, 0x6B, 0x45, 0x74, 0x27, 0x16, 0x81,
-            0xB0, 0xE3, 0xD2, 0xBF, 0x8E, 0xDD, 0xEC, 0x7B, 0x4A, 0x19, 0x28,
-            0x06, 0x37, 0x64, 0x55, 0xC2, 0xF3, 0xA0, 0x91, 0x47, 0x76, 0x25,
-            0x14, 0x83, 0xB2, 0xE1, 0xD0, 0xFE, 0xCF, 0x9C, 0xAD, 0x3A, 0x0B,
-            0x58, 0x69, 0x04, 0x35, 0x66, 0x57, 0xC0, 0xF1, 0xA2, 0x93, 0xBD,
-            0x8C, 0xDF, 0xEE, 0x79, 0x48, 0x1B, 0x2A, 0xC1, 0xF0, 0xA3, 0x92,
-            0x05, 0x34, 0x67, 0x56, 0x78, 0x49, 0x1A, 0x2B, 0xBC, 0x8D, 0xDE,
-            0xEF, 0x82, 0xB3, 0xE0, 0xD1, 0x46, 0x77, 0x24, 0x15, 0x3B, 0x0A,
-            0x59, 0x68, 0xFF, 0xCE, 0x9D, 0xAC };
+        private int[] initTable16() {
+            int[] table = new int[256];
+            int crc;
+            for (int i = 0; i < 256; i++) {
+                crc = i << 8;
+                for (int j = 0; j < 8; j++) {
+                    boolean bit = (crc & 0x8000) != 0;
+                    crc <<= 1;
+                    if (bit) {
+                        crc ^= poly;
+                    }
+                }
+                table[i] = crc & 0xFFFF;
+            }
+            return table;
+        }
 
-    // More info: http://reveng.sourceforge.net/crc-catalogue/16.htm
-    public static final String CRC16_IBM = "IBM";
-    public static final String CRC16_MODBUS = "MODBUS";
-    public static final String CRC16_X25 = "X-25";
-    public static final String CRC16_CCITT_FALSE = "CCITT-FALSE";
-    public static final String CRC16_KERMIT = "KERMIT";
-    public static final String CRC16_XMODEM = "XMODEM";
-    public static final String CRC16_AUG_CCITT = "AUG-CCITT";
-    public static final String CRC16_GENIBUS = "GENIBUS";
-    public static final String CRC16_MCRF4XX = "MCRF4XX";
+    }
 
-    private static int crc16Unreflected(ByteBuffer buf, int crcIn, int[] table) {
-        int crc16 = crcIn;
-        while (buf.hasRemaining()) {
-            crc16 = table[((crc16 >> 8) ^ buf.get()) & 0xff] ^ (crc16 << 8);
+    private static int reverse(int value, int bits) {
+        int result = 0;
+        for (int i = 0; i < bits; i++) {
+            result = (result << 1) | (value & 1);
+            value >>= 1;
         }
-        return crc16 & 0xFFFF;
+        return result;
     }
 
-    private static int crc16Reflected(ByteBuffer buf, int crcIn, int[] table) {
-        int crc16 = crcIn;
+    public static int crc8(Algorithm algorithm, ByteBuffer buf) {
+        int crc = algorithm.init;
         while (buf.hasRemaining()) {
-            crc16 = table[(crc16 ^ buf.get()) & 0xff] ^ (crc16 >> 8);
+            int b = buf.get() & 0xFF;
+            if (algorithm.refIn) {
+                b = reverse(b, 8);
+            }
+            crc = algorithm.table[(crc & 0xFF) ^ b];
         }
-        return crc16 & 0xFFFF;
-    }
-
-    public static int crc16(String type, ByteBuffer buf) {
-        switch (type) {
-            case CRC16_IBM:
-                return crc16Reflected(buf, 0, CRC16_IBM_TABLE);
-            case CRC16_MODBUS:
-                return crc16Reflected(buf, 0xFFFF, CRC16_IBM_TABLE);
-            case CRC16_X25:
-                return crc16Reflected(buf, 0xFFFF, CRC16_CCITT_TABLE_REVERSE) ^ 0xFFFF;
-            case CRC16_CCITT_FALSE:
-                return crc16Unreflected(buf, 0xFFFF, CRC16_CCITT_TABLE);
-            case CRC16_KERMIT:
-                return crc16Reflected(buf, 0, CRC16_CCITT_TABLE_REVERSE);
-            case CRC16_XMODEM:
-                return crc16Unreflected(buf, 0, CRC16_CCITT_TABLE);
-            case CRC16_AUG_CCITT:
-                return crc16Unreflected(buf, 0x1d0f, CRC16_CCITT_TABLE);
-            case CRC16_GENIBUS:
-                return crc16Unreflected(buf, 0xFFFF, CRC16_CCITT_TABLE) ^ 0xFFFF;
-            case CRC16_MCRF4XX:
-                return crc16Reflected(buf, 0xFFFF, CRC16_CCITT_TABLE_REVERSE);
-            default:
-                throw new UnsupportedOperationException(type);
+        if (algorithm.refOut) {
+            crc = reverse(crc, 8);
         }
+        return (crc ^ algorithm.xorOut) & 0xFF;
     }
 
-    public static int crc8(ByteBuffer buf) {
-        int crc = 0xFF;
+    public static int crc16(Algorithm algorithm, ByteBuffer buf) {
+        int crc = algorithm.init;
         while (buf.hasRemaining()) {
-            crc = CRC8_TABLE[(crc ^ buf.get()) & 0xFF];
+            int b = buf.get() & 0xFF;
+            if (algorithm.refIn) {
+                b = reverse(b, 8);
+            }
+            crc = (crc << 8) ^ algorithm.table[((crc >> 8) & 0xFF) ^ b];
+        }
+        if (algorithm.refOut) {
+            crc = reverse(crc, 16);
         }
-        return crc & 0xFF;
+        return (crc ^ algorithm.xorOut) & 0xFFFF;
     }
 
+    public static final Algorithm CRC8_EGTS = new Algorithm(8, 0x31, 0xFF, false, false, 0x00);
+    public static final Algorithm CRC8_ROHC = new Algorithm(8, 0x07, 0xFF, true, true, 0x00);
+
+    public static final Algorithm CRC16_IBM = new Algorithm(16, 0x8005, 0x0000, true, true, 0x0000);
+    public static final Algorithm CRC16_X25 = new Algorithm(16, 0x1021, 0xFFFF, true, true, 0xFFFF);
+    public static final Algorithm CRC16_MODBUS = new Algorithm(16, 0x8005, 0xFFFF, true, true, 0x0000);
+    public static final Algorithm CRC16_CCITT_FALSE = new Algorithm(16, 0x1021, 0xFFFF, false, false, 0x0000);
+    public static final Algorithm CRC16_KERMIT = new Algorithm(16, 0x1021, 0x0000, true, true, 0x0000);
+    public static final Algorithm CRC16_XMODEM = new Algorithm(16, 0x1021, 0x0000, false, false, 0x0000);
+
     public static int crc32(ByteBuffer buf) {
         CRC32 checksum = new CRC32();
         while (buf.hasRemaining()) {
diff --git a/src/org/traccar/protocol/EgtsProtocolDecoder.java b/src/org/traccar/protocol/EgtsProtocolDecoder.java
index 85376b1a5..fe82a51ed 100644
--- a/src/org/traccar/protocol/EgtsProtocolDecoder.java
+++ b/src/org/traccar/protocol/EgtsProtocolDecoder.java
@@ -97,7 +97,7 @@ public class EgtsProtocolDecoder extends BaseProtocolDecoder {
             response.writeShort(record.readableBytes());
             response.writeShort(packetId++);
             response.writeByte(packetType);
-            response.writeByte(Checksum.crc8(response.toByteBuffer()));
+            response.writeByte(Checksum.crc8(Checksum.CRC8_EGTS, response.toByteBuffer()));
             response.writeBytes(record);
             response.writeShort(recordChecksum);