Java tutorial
/* * Copyright 2017 - 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. * 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.DateBuilder; import org.traccar.helper.UnitsConverter; import org.traccar.model.Position; import java.net.SocketAddress; import java.nio.charset.StandardCharsets; public class Gps056ProtocolDecoder extends BaseProtocolDecoder { public Gps056ProtocolDecoder(Protocol protocol) { super(protocol); } private static void sendResponse(Channel channel, String type, String imei, ByteBuf content) { if (channel != null) { ByteBuf response = Unpooled.buffer(); String header = "*" + type + imei; response.writeBytes(header.getBytes(StandardCharsets.US_ASCII)); if (content != null) { response.writeBytes(content); } response.writeByte('#'); channel.writeAndFlush(new NetworkMessage(response, channel.remoteAddress())); } } private static double decodeCoordinate(ByteBuf buf) { double degrees = buf.getUnsignedShort(buf.readerIndex()) / 100; double minutes = buf.readUnsignedShort() % 100 + buf.readUnsignedShort() * 0.0001; degrees += minutes / 60; byte hemisphere = buf.readByte(); if (hemisphere == 'S' || hemisphere == 'W') { degrees = -degrees; } return degrees; } private static void decodeStatus(ByteBuf buf, Position position) { position.set(Position.KEY_INPUT, buf.readUnsignedByte()); position.set(Position.KEY_OUTPUT, buf.readUnsignedByte()); position.set(Position.PREFIX_ADC + 1, buf.readShortLE() * 5.06); // mV position.set(Position.KEY_SATELLITES, buf.readUnsignedByte()); position.set(Position.KEY_RSSI, buf.readUnsignedByte()); } @Override protected Object decode(Channel channel, SocketAddress remoteAddress, Object msg) throws Exception { ByteBuf buf = (ByteBuf) msg; buf.skipBytes(2); // header buf.skipBytes(2); // length String type = buf.readSlice(7).toString(StandardCharsets.US_ASCII); String imei = buf.readSlice(15).toString(StandardCharsets.US_ASCII); DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, imei); if (deviceSession == null) { return null; } if (type.startsWith("LOGN")) { ByteBuf content = Unpooled.copiedBuffer("1", StandardCharsets.US_ASCII); try { sendResponse(channel, "LGSA" + type.substring(4), imei, content); } finally { content.release(); } } else if (type.startsWith("GPSL")) { Position position = new Position(getProtocolName()); position.setDeviceId(deviceSession.getDeviceId()); DateBuilder dateBuilder = new DateBuilder() .setDateReverse(buf.readUnsignedByte(), buf.readUnsignedByte(), buf.readUnsignedByte()) .setTime(buf.readUnsignedByte(), buf.readUnsignedByte(), buf.readUnsignedByte()); position.setValid(true); position.setTime(dateBuilder.getDate()); position.setLatitude(decodeCoordinate(buf)); position.setLongitude(decodeCoordinate(buf)); position.setSpeed(UnitsConverter.knotsFromKph(buf.readUnsignedByte())); position.setCourse(buf.readUnsignedShort()); decodeStatus(buf, position); sendResponse(channel, "GPSA" + type.substring(4), imei, buf.readSlice(2)); return position; } else if (type.startsWith("SYNC")) { Position position = new Position(getProtocolName()); position.setDeviceId(deviceSession.getDeviceId()); getLastLocation(position, null); decodeStatus(buf, position); sendResponse(channel, "SYSA" + type.substring(4), imei, null); return position; } return null; } }