aboutsummaryrefslogtreecommitdiff
path: root/src/org/traccar/protocol/NavisProtocolDecoder.java
blob: 7ba474ae046fe772eef395044e13348ca4db4d8f (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
/*
 * Copyright 2012 - 2019 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.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.traccar.protocol;

import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.Channel;
import org.traccar.BaseProtocolDecoder;
import org.traccar.DeviceSession;
import org.traccar.NetworkMessage;
import org.traccar.Protocol;
import org.traccar.helper.BitUtil;
import org.traccar.helper.Checksum;
import org.traccar.helper.Checksum.Algorithm;
import org.traccar.helper.DateBuilder;
import org.traccar.helper.UnitsConverter;
import org.traccar.model.Position;

import java.net.SocketAddress;
import java.nio.charset.StandardCharsets;
import java.util.LinkedList;
import java.util.List;
import java.util.Date;

public class NavisProtocolDecoder extends BaseProtocolDecoder {

    private static final int[] FLEX_FIELDS_SIZES = {
            4, 2, 4, 1, 1, 1, 1, 1, 4, 4, 4, 4, 4, 2, 4, 4, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 1, 1, 1, 1, 4, 4, 2, 2,
            4, 2, 2, 2, 2, 2, 2, 2, 1, 1, 1, 1, 1, 1, 1, 1, 2, 4, 2, 1, 4, 2, 2, 2, 2, 2, 1, 1, 1, 2, 4, 2, 1,
            /* FLEX 2.0 */
            8, 2, 1, 16, 4, 2, 4, 37, 1, 1, 1, 1, 1, 1, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 6, 12, 24, 48, 1, 1, 1, 1, 4, 4,
            1, 4, 2, 6, 2, 6, 2, 2, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 1
    };

    private String prefix;
    private long deviceUniqueId, serverId;
    private int flexDataSize;
    private int flexBitFieldSize;
    private final byte[] flexBitField = new byte[16];

    public NavisProtocolDecoder(Protocol protocol) {
        super(protocol);
    }

    public static final int F10 = 0x01;
    public static final int F20 = 0x02;
    public static final int F30 = 0x03;
    public static final int F40 = 0x04;
    public static final int F50 = 0x05;
    public static final int F51 = 0x15;
    public static final int F52 = 0x25;
    public static final int F60 = 0x06;

    public int getFlexDataSize() {
        return flexDataSize;
    }

    private static boolean isFormat(int type, int... types) {
        for (int i : types) {
            if (type == i) {
                return true;
            }
        }
        return false;
    }

    private Position parseNtcbPosition(DeviceSession deviceSession, ByteBuf buf) {
        Position position = new Position(getProtocolName());

        position.setDeviceId(deviceSession.getDeviceId());

        int format;
        if (buf.getUnsignedByte(buf.readerIndex()) == 0) {
            format = buf.readUnsignedShortLE();
        } else {
            format = buf.readUnsignedByte();
        }
        position.set("format", format);

        position.set(Position.KEY_INDEX, buf.readUnsignedIntLE());
        position.set(Position.KEY_EVENT, buf.readUnsignedShortLE());

        buf.skipBytes(6); // event time

        short armedStatus = buf.readUnsignedByte();
        if (isFormat(format, F10, F20, F30, F40, F50, F51, F52)) {
            position.set(Position.KEY_ARMED, BitUtil.to(armedStatus, 7));
            if (BitUtil.check(armedStatus, 7)) {
                position.set(Position.KEY_ALARM, Position.ALARM_GENERAL);
            }
        } else if (isFormat(format, F60)) {
            position.set(Position.KEY_ARMED, BitUtil.check(armedStatus, 0));
            if (BitUtil.check(armedStatus, 1)) {
                position.set(Position.KEY_ALARM, Position.ALARM_GENERAL);
            }
        }

        position.set(Position.KEY_STATUS, buf.readUnsignedByte());
        position.set(Position.KEY_RSSI, buf.readUnsignedByte());

        if (isFormat(format, F10, F20, F30)) {
            int output = buf.readUnsignedShortLE();
            position.set(Position.KEY_OUTPUT, output);
            for (int i = 0; i < 16; i++) {
                position.set(Position.PREFIX_OUT + (i + 1), BitUtil.check(output, i));
            }
        } else if (isFormat(format, F50, F51, F52)) {
            short extField = buf.readUnsignedByte();
            position.set(Position.KEY_OUTPUT, BitUtil.to(extField, 2));
            position.set(Position.PREFIX_OUT + 1, BitUtil.check(extField, 0));
            position.set(Position.PREFIX_OUT + 2, BitUtil.check(extField, 1));
            position.set(Position.KEY_SATELLITES, BitUtil.from(extField, 2));
        } else if (isFormat(format, F40, F60)) {
            short output = buf.readUnsignedByte();
            position.set(Position.KEY_OUTPUT, BitUtil.to(output, 4));
            for (int i = 0; i < 4; i++) {
                position.set(Position.PREFIX_OUT + (i + 1), BitUtil.check(output, i));
            }
        }

        if (isFormat(format, F10, F20, F30, F40)) {
            int input = buf.readUnsignedShortLE();
            position.set(Position.KEY_INPUT, input);
            if (!isFormat(format, F40)) {
                for (int i = 0; i < 16; i++) {
                    position.set(Position.PREFIX_IN + (i + 1), BitUtil.check(input, i));
                }
            } else {
                position.set(Position.PREFIX_IN + 1, BitUtil.check(input, 0));
                position.set(Position.PREFIX_IN + 2, BitUtil.check(input, 1));
                position.set(Position.PREFIX_IN + 3, BitUtil.check(input, 2));
                position.set(Position.PREFIX_IN + 4, BitUtil.check(input, 3));
                position.set(Position.PREFIX_IN + 5, BitUtil.between(input, 4, 7));
                position.set(Position.PREFIX_IN + 6, BitUtil.between(input, 7, 10));
                position.set(Position.PREFIX_IN + 7, BitUtil.between(input, 10, 12));
                position.set(Position.PREFIX_IN + 8, BitUtil.between(input, 12, 14));
            }
        } else if (isFormat(format, F50, F51, F52, F60)) {
            short input = buf.readUnsignedByte();
            position.set(Position.KEY_INPUT, input);
            for (int i = 0; i < 8; i++) {
                position.set(Position.PREFIX_IN + (i + 1), BitUtil.check(input, i));
            }
        }

        position.set(Position.KEY_POWER, buf.readUnsignedShortLE() * 0.001);
        position.set(Position.KEY_BATTERY, buf.readUnsignedShortLE() * 0.001);

        if (isFormat(format, F10, F20, F30)) {
            position.set(Position.PREFIX_TEMP + 1, buf.readShortLE());
        }

        if (isFormat(format, F10, F20, F50, F51, F52, F60)) {
            position.set(Position.PREFIX_ADC + 1, buf.readUnsignedShortLE());
            position.set(Position.PREFIX_ADC + 2, buf.readUnsignedShortLE());
        }
        if (isFormat(format, F60)) {
            position.set(Position.PREFIX_ADC + 3, buf.readUnsignedShortLE());
        }

        // Impulse counters
        if (isFormat(format, F20, F50, F51, F52, F60)) {
            buf.readUnsignedIntLE();
            buf.readUnsignedIntLE();
        }

        if (isFormat(format, F60)) {
            // Fuel
            buf.readUnsignedShortLE();
            buf.readUnsignedShortLE();
            buf.readByte();
            buf.readShortLE();
            buf.readByte();
            buf.readUnsignedShortLE();
            buf.readByte();
            buf.readUnsignedShortLE();
            buf.readByte();
            buf.readUnsignedShortLE();
            buf.readByte();
            buf.readUnsignedShortLE();
            buf.readByte();
            buf.readUnsignedShortLE();
            buf.readByte();
            buf.readUnsignedShortLE();
            buf.readByte();
            buf.readUnsignedShortLE();

            position.set(Position.PREFIX_TEMP + 1, buf.readByte());
            position.set(Position.PREFIX_TEMP + 2, buf.readByte());
            position.set(Position.PREFIX_TEMP + 3, buf.readByte());
            position.set(Position.PREFIX_TEMP + 4, buf.readByte());
            position.set(Position.KEY_AXLE_WEIGHT, buf.readIntLE());
            position.set(Position.KEY_RPM, buf.readUnsignedShortLE());
        }

        if (isFormat(format, F20, F50, F51, F52, F60)) {
            int navSensorState = buf.readUnsignedByte();
            position.setValid(BitUtil.check(navSensorState, 1));
            if (isFormat(format, F60)) {
                position.set(Position.KEY_SATELLITES, BitUtil.from(navSensorState, 2));
            }

            DateBuilder dateBuilder = new DateBuilder()
                    .setTime(buf.readUnsignedByte(), buf.readUnsignedByte(), buf.readUnsignedByte())
                    .setDateReverse(buf.readUnsignedByte(), buf.readUnsignedByte() + 1, buf.readUnsignedByte());
            position.setTime(dateBuilder.getDate());

            if (isFormat(format, F60)) {
                position.setLatitude(buf.readIntLE() / 600000.0);
                position.setLongitude(buf.readIntLE() / 600000.0);
                position.setAltitude(buf.readIntLE() * 0.1);
            } else {
                position.setLatitude(buf.readFloatLE() / Math.PI * 180);
                position.setLongitude(buf.readFloatLE() / Math.PI * 180);
            }

            position.setSpeed(UnitsConverter.knotsFromKph(buf.readFloatLE()));
            position.setCourse(buf.readUnsignedShortLE());

            position.set(Position.KEY_ODOMETER, buf.readFloatLE() * 1000);
            position.set(Position.KEY_DISTANCE, buf.readFloatLE() * 1000);

            // Segment times
            buf.readUnsignedShortLE();
            buf.readUnsignedShortLE();
        }

        // Other
        if (isFormat(format, F51, F52)) {
            buf.readUnsignedShortLE();
            buf.readByte();
            buf.readUnsignedShortLE();
            buf.readUnsignedShortLE();
            buf.readByte();
            buf.readUnsignedShortLE();
            buf.readUnsignedShortLE();
            buf.readByte();
            buf.readUnsignedShortLE();
        }

        // Four temperature sensors
        if (isFormat(format, F40, F52)) {
            position.set(Position.PREFIX_TEMP + 1, buf.readByte());
            position.set(Position.PREFIX_TEMP + 2, buf.readByte());
            position.set(Position.PREFIX_TEMP + 3, buf.readByte());
            position.set(Position.PREFIX_TEMP + 4, buf.readByte());
        }

        return position;
    }

    private Object processNtcbSingle(DeviceSession deviceSession, Channel channel, ByteBuf buf) {
        Position position = parseNtcbPosition(deviceSession, buf);

        ByteBuf response = Unpooled.buffer(7);
        response.writeCharSequence("*<T", StandardCharsets.US_ASCII);
        response.writeIntLE((int) position.getLong(Position.KEY_INDEX));
        sendNtcbReply(channel, response);

        return position.getFixTime() != null ? position : null;
    }

    private Object processNtcbArray(DeviceSession deviceSession, Channel channel, ByteBuf buf) {
        List<Position> positions = new LinkedList<>();
        int count = buf.readUnsignedByte();

        for (int i = 0; i < count; i++) {
            Position position = parseNtcbPosition(deviceSession, buf);
            if (position.getFixTime() != null) {
                positions.add(position);
            }
        }

        ByteBuf response = Unpooled.buffer(7);
        response.writeCharSequence("*<A", StandardCharsets.US_ASCII);
        response.writeByte(count);
        sendNtcbReply(channel, response);

        if (positions.isEmpty()) {
            return null;
        }

        return positions;
    }

    private boolean checkFlexBitfield(int index) {
        int byteIndex = Math.floorDiv(index, 8);
        int bitIndex = Math.floorMod(index, 8);
        return BitUtil.check(flexBitField[byteIndex], 7 - bitIndex);
    }

    private Position parseFlexPosition(DeviceSession deviceSession, ByteBuf buf) {

        Position position = new Position(getProtocolName());

        position.setDeviceId(deviceSession.getDeviceId());

        int status = 0;
        short input = 0;
        short output = 0;

        for (int i = 0; i < flexBitFieldSize; i++) {
            if (!checkFlexBitfield(i)) {
                continue;
            }

            switch (i) {
                case 0:
                    position.set(Position.KEY_INDEX, buf.readUnsignedIntLE());
                    break;
                case 1:
                    position.set(Position.KEY_EVENT, buf.readUnsignedShortLE());
                    break;
                case 3:
                    short armedStatus = buf.readUnsignedByte();
                    position.set(Position.KEY_ARMED, BitUtil.check(armedStatus, 0));
                    if (BitUtil.check(armedStatus, 1)) {
                        position.set(Position.KEY_ALARM, Position.ALARM_GENERAL);
                    }
                    break;
                case 4:
                    status = buf.readUnsignedByte();
                    position.set(Position.KEY_STATUS, status);
                    break;
                case 5:
                    int status2 = buf.readUnsignedByte();
                    position.set(Position.KEY_STATUS, (short) (BitUtil.to(status, 8) | (status2 << 8)));
                    break;
                case 6:
                    position.set(Position.KEY_RSSI, buf.readUnsignedByte());
                    break;
                case 7:
                    int navSensorState = buf.readUnsignedByte();
                    position.setValid(BitUtil.check(navSensorState, 1));
                    position.set(Position.KEY_SATELLITES, BitUtil.from(navSensorState, 2));
                    break;
                case 8:
                     position.setTime(new DateBuilder(new Date(buf.readUnsignedIntLE() * 1000)).getDate());
                    break;
                case 9:
                    position.setLatitude(buf.readIntLE() / 600000.0);
                    break;
                case 10:
                    position.setLongitude(buf.readIntLE() / 600000.0);
                    break;
                case 11:
                    position.setAltitude(buf.readIntLE() * 0.1);
                    break;
                case 12:
                    position.setSpeed(UnitsConverter.knotsFromKph(buf.readFloatLE()));
                    break;
                case 13:
                    position.setCourse(buf.readUnsignedShortLE());
                    break;
                case 14:
                    position.set(Position.KEY_ODOMETER, buf.readFloatLE() * 1000);
                    break;
                case 15:
                    position.set(Position.KEY_DISTANCE, buf.readFloatLE() * 1000);
                    break;
                case 18:
                    position.set(Position.KEY_POWER, buf.readUnsignedShortLE() * 0.001);
                    break;
                case 19:
                    position.set(Position.KEY_BATTERY, buf.readUnsignedShortLE() * 0.001);
                    break;
                case 20:
                case 21:
                case 22:
                case 23:
                case 24:
                case 25:
                case 26:
                case 27:
                    position.set(Position.PREFIX_ADC + (i - 19), buf.readUnsignedShortLE());
                    break;
                case 28:
                    input = buf.readUnsignedByte();
                    position.set(Position.KEY_INPUT, input);
                    for (int k = 0; k < 8; k++) {
                        position.set(Position.PREFIX_IN + (k + 1), BitUtil.check(input, k));
                    }
                    break;
                case 29:
                    short input2 = buf.readUnsignedByte();
                    position.set(Position.KEY_INPUT, (short) (BitUtil.to(input, 8) | (input2 << 8)));
                    for (int k = 0; k < 8; k++) {
                        position.set(Position.PREFIX_IN + (k + 9), BitUtil.check(input2, k));
                    }
                    break;
                case 30:
                    output = buf.readUnsignedByte();
                    position.set(Position.KEY_OUTPUT, output);
                    for (int k = 0; k < 8; k++) {
                        position.set(Position.PREFIX_OUT + (k + 1), BitUtil.check(output, k));
                    }
                    break;
                case 31:
                    short output2 = buf.readUnsignedByte();
                    position.set(Position.KEY_OUTPUT, (short) (BitUtil.to(output, 8) | (output2 << 8)));
                    for (int k = 0; k < 8; k++) {
                        position.set(Position.PREFIX_OUT + (k + 9), BitUtil.check(output2, k));
                    }
                    break;
                case 36:
                    position.set(Position.KEY_HOURS, buf.readUnsignedIntLE() * 1000);
                    break;
                case 44:
                case 45:
                case 46:
                case 47:
                case 48:
                case 49:
                case 50:
                case 51:
                    position.set(Position.PREFIX_TEMP + (i - 43), buf.readByte());
                    break;
                case 68:
                    position.set("can-speed", buf.readUnsignedByte());
                    break;
                // FLEX 2.0
                case 69:
                    int satVisible = 0;
                    for (int k = 0; k < 8; k++) {
                        satVisible += buf.readUnsignedByte();
                    }
                    position.set(Position.KEY_SATELLITES_VISIBLE, satVisible);
                    break;
                case 70:
                    position.set(Position.KEY_HDOP, buf.readUnsignedByte() * 0.1);
                    position.set(Position.KEY_PDOP, buf.readUnsignedByte() * 0.1);
                    break;
                default:
                    if (i < FLEX_FIELDS_SIZES.length) {
                        buf.skipBytes(FLEX_FIELDS_SIZES[i]);
                    }
                    break;
            }
        }

        return position;
    }

    private Position parseFlex20Position(DeviceSession deviceSession, ByteBuf buf) {

        Position position = new Position(getProtocolName());
        position.setDeviceId(deviceSession.getDeviceId());

        int length = buf.readUnsignedShort();
        if (length <= buf.readableBytes() && buf.readUnsignedByte() == 0x0A) {

            buf.readUnsignedByte(); // length of static part

            position.set(Position.KEY_INDEX, buf.readUnsignedIntLE());

            position.set(Position.KEY_EVENT, buf.readUnsignedShortLE());
            buf.readUnsignedInt(); // event time

            int navSensorState = buf.readUnsignedByte();
            position.setValid(BitUtil.check(navSensorState, 1));
            position.set(Position.KEY_SATELLITES, BitUtil.from(navSensorState, 2));

            position.setTime(new DateBuilder(new Date(buf.readUnsignedIntLE() * 1000)).getDate());
            position.setLatitude(buf.readIntLE() / 600000.0);
            position.setLongitude(buf.readIntLE() / 600000.0);
            position.setAltitude(buf.readIntLE() * 0.1);
            position.setSpeed(UnitsConverter.knotsFromKph(buf.readFloatLE()));
            position.setCourse(buf.readUnsignedShortLE());
            position.set(Position.KEY_ODOMETER, buf.readFloatLE() * 1000);

            buf.skipBytes(length - buf.readerIndex() - 1); // skip unused part
        }

        return position;
    }

    private interface FlexPositionParser {
        Position parsePosition(DeviceSession deviceSession, ByteBuf buf);
    }

    private Object processFlexSingle(
            FlexPositionParser parser, String flexHeader, DeviceSession deviceSession, Channel channel, ByteBuf buf) {

        if (!flexHeader.equals("~C")) {
            buf.readUnsignedInt(); // event index
        }

        Position position = parser.parsePosition(deviceSession, buf);

        ByteBuf response = Unpooled.buffer();
        response.writeCharSequence(flexHeader, StandardCharsets.US_ASCII);
        response.writeIntLE((int) position.getLong(Position.KEY_INDEX));
        sendFlexReply(channel, response);

        return position.getFixTime() != null ? position : null;
    }

    private Object processFlexArray(
            FlexPositionParser parser, String flexHeader, DeviceSession deviceSession, Channel channel, ByteBuf buf) {

        List<Position> positions = new LinkedList<>();
        int count = buf.readUnsignedByte();

        for (int i = 0; i < count; i++) {
            Position position = parser.parsePosition(deviceSession, buf);
            if (position.getFixTime() != null) {
                positions.add(position);
            }
        }

        ByteBuf response = Unpooled.buffer();
        response.writeCharSequence(flexHeader, StandardCharsets.US_ASCII);
        response.writeByte(count);
        sendFlexReply(channel, response);

        return !positions.isEmpty() ? positions : null;
    }

    private Object processFlexNegotiation(Channel channel, ByteBuf buf) {
        if ((byte) buf.readUnsignedByte() != (byte) 0xB0) {
            return null;
        }

        short flexProtocolVersion = buf.readUnsignedByte();
        short flexStructVersion = buf.readUnsignedByte();
        if ((flexProtocolVersion == 0x0A || flexProtocolVersion == 0x14)
            && (flexStructVersion == 0x0A || flexStructVersion == 0x14)) {

            flexBitFieldSize = buf.readUnsignedByte();
            if (flexBitFieldSize > 122) {
                return null;
            }

            buf.readBytes(flexBitField, 0, (int) Math.ceil((double) flexBitFieldSize / 8));

            flexDataSize = 0;
            for (int i = 0; i < flexBitFieldSize; i++) {
                if (checkFlexBitfield(i)) {
                    flexDataSize += FLEX_FIELDS_SIZES[i];
                }
            }
        } else {
            flexProtocolVersion = 0x14;
            flexStructVersion = 0x14;
        }

        ByteBuf response = Unpooled.buffer(9);
        response.writeCharSequence("*<FLEX", StandardCharsets.US_ASCII);
        response.writeByte(0xB0);
        response.writeByte(flexProtocolVersion);
        response.writeByte(flexStructVersion);
        sendNtcbReply(channel, response);

        return null;
    }

    private Object processHandshake(Channel channel, SocketAddress remoteAddress, ByteBuf buf) {
        buf.readByte(); // colon
        if (getDeviceSession(channel, remoteAddress, buf.toString(StandardCharsets.US_ASCII)) != null) {
            sendNtcbReply(channel, Unpooled.copiedBuffer("*<S", StandardCharsets.US_ASCII));
        }
        return null;
    }

    private void sendNtcbReply(Channel channel, ByteBuf data) {
        if (channel != null) {
            ByteBuf header = Unpooled.buffer(16);
            header.writeCharSequence(prefix, StandardCharsets.US_ASCII);
            header.writeIntLE((int) deviceUniqueId);
            header.writeIntLE((int) serverId);
            header.writeShortLE(data.readableBytes());
            header.writeByte(Checksum.xor(data.nioBuffer()));
            header.writeByte(Checksum.xor(header.nioBuffer()));

            channel.writeAndFlush(new NetworkMessage(Unpooled.wrappedBuffer(header, data), channel.remoteAddress()));
        }
    }

    private void sendFlexReply(Channel channel, ByteBuf data) {
        if (channel != null) {
            ByteBuf cs = Unpooled.buffer(1);
            cs.writeByte(Checksum.crc8(new Algorithm(8, 0x31, 0xFF, false, false, 0x00), data.nioBuffer()));

            channel.writeAndFlush(new NetworkMessage(Unpooled.wrappedBuffer(data, cs), channel.remoteAddress()));
        }
    }

    private Object decodeNtcb(Channel channel, SocketAddress remoteAddress, ByteBuf buf) {

        prefix = buf.toString(buf.readerIndex(), 4, StandardCharsets.US_ASCII);
        buf.skipBytes(prefix.length()); // prefix @NTC by default
        serverId = buf.readUnsignedIntLE();
        deviceUniqueId = buf.readUnsignedIntLE();
        int length = buf.readUnsignedShortLE();
        buf.skipBytes(2); // header and data XOR checksum

        if (length == 0) {
            return null; // keep alive message
        }

        String type = buf.toString(buf.readerIndex(), 3, StandardCharsets.US_ASCII);
        buf.skipBytes(type.length());

        if (type.equals("*>S")) {
            return processHandshake(channel, remoteAddress, buf);
        } else {
            DeviceSession deviceSession = getDeviceSession(channel, remoteAddress);
            if (deviceSession != null) {
                switch (type) {
                    case "*>A":
                        return processNtcbArray(deviceSession, channel, buf);
                    case "*>T":
                        return processNtcbSingle(deviceSession, channel, buf);
                    case "*>F":
                        buf.skipBytes(3);
                        return processFlexNegotiation(channel, buf);
                    default:
                        break;
                }
            }
        }

        return null;
    }

    private Object decodeFlex(Channel channel, SocketAddress remoteAddress, ByteBuf buf) {

        if (buf.getByte(buf.readerIndex()) == 0x7F) {
            return null; // keep alive
        }

        String type = buf.toString(buf.readerIndex(), 2, StandardCharsets.US_ASCII);
        buf.skipBytes(type.length());

        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress);
        if (deviceSession != null) {
            switch (type) {
                // FLEX 1.0
                case "~A":
                    return processFlexArray(this::parseFlexPosition, type, deviceSession, channel, buf);
                case "~T":
                case "~C":
                    return processFlexSingle(this::parseFlexPosition, type, deviceSession, channel, buf);
                // FLEX 2.0 (extra packages)
                case "~E":
                    return processFlexArray(this::parseFlex20Position, type, deviceSession, channel, buf);
                case "~X":
                    return processFlexSingle(this::parseFlex20Position, type, deviceSession, channel, buf);
                default:
                    break;
            }
        }

        return null;
    }

    @Override
    protected Object decode(
            Channel channel, SocketAddress remoteAddress, Object msg) throws Exception {

        ByteBuf buf = (ByteBuf) msg;

        if (flexDataSize > 0) {
            return decodeFlex(channel, remoteAddress, buf);
        } else {
            return decodeNtcb(channel, remoteAddress, buf);
        }
    }

}