Java tutorial
/* * Copyright 2016 - 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 org.traccar.BaseProtocolEncoder; import org.traccar.helper.DataConverter; import org.traccar.model.Command; import java.nio.ByteBuffer; import java.nio.charset.StandardCharsets; public class EelinkProtocolEncoder extends BaseProtocolEncoder { private boolean connectionless; public EelinkProtocolEncoder(boolean connectionless) { this.connectionless = connectionless; } public static int checksum(ByteBuffer buf) { int sum = 0; while (buf.hasRemaining()) { sum = (((sum << 1) | (sum >> 15)) + (buf.get() & 0xFF)) & 0xFFFF; } return sum; } public static ByteBuf encodeContent(boolean connectionless, String uniqueId, int type, int index, ByteBuf content) { ByteBuf buf = Unpooled.buffer(); if (connectionless) { buf.writeBytes(DataConverter.parseHex('0' + uniqueId)); } buf.writeByte(0x67); buf.writeByte(0x67); buf.writeByte(type); buf.writeShort(2 + (content != null ? content.readableBytes() : 0)); // length buf.writeShort(index); if (content != null) { buf.writeBytes(content); } ByteBuf result = Unpooled.buffer(); if (connectionless) { result.writeByte('E'); result.writeByte('L'); result.writeShort(2 + buf.readableBytes()); // length result.writeShort(checksum(buf.nioBuffer())); } result.writeBytes(buf); buf.release(); return result; } private ByteBuf encodeContent(long deviceId, String content) { ByteBuf buf = Unpooled.buffer(); buf.writeByte(0x01); // command buf.writeInt(0); // server id buf.writeBytes(content.getBytes(StandardCharsets.UTF_8)); return encodeContent(connectionless, getUniqueId(deviceId), EelinkProtocolDecoder.MSG_DOWNLINK, 0, buf); } @Override protected Object encodeCommand(Command command) { switch (command.getType()) { case Command.TYPE_CUSTOM: return encodeContent(command.getDeviceId(), command.getString(Command.KEY_DATA)); case Command.TYPE_POSITION_SINGLE: return encodeContent(command.getDeviceId(), "WHERE#"); case Command.TYPE_ENGINE_STOP: return encodeContent(command.getDeviceId(), "RELAY,1#"); case Command.TYPE_ENGINE_RESUME: return encodeContent(command.getDeviceId(), "RELAY,0#"); case Command.TYPE_REBOOT_DEVICE: return encodeContent(command.getDeviceId(), "RESET#"); default: return null; } } }