Java tutorial
/* * Copyright 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.Context; import org.traccar.helper.Checksum; import org.traccar.model.Command; import java.nio.charset.StandardCharsets; public class CastelProtocolEncoder extends BaseProtocolEncoder { private ByteBuf encodeContent(long deviceId, short type, ByteBuf content) { ByteBuf buf = Unpooled.buffer(0); String uniqueId = Context.getIdentityManager().getById(deviceId).getUniqueId(); buf.writeByte('@'); buf.writeByte('@'); buf.writeShortLE(2 + 2 + 1 + 20 + 2 + content.readableBytes() + 2 + 2); // length buf.writeByte(1); // protocol version buf.writeBytes(uniqueId.getBytes(StandardCharsets.US_ASCII)); buf.writeZero(20 - uniqueId.length()); buf.writeShort(type); buf.writeBytes(content); buf.writeShortLE(Checksum.crc16(Checksum.CRC16_X25, buf.nioBuffer())); buf.writeByte('\r'); buf.writeByte('\n'); return buf; } @Override protected Object encodeCommand(Command command) { ByteBuf content = Unpooled.buffer(0); switch (command.getType()) { case Command.TYPE_ENGINE_STOP: content.writeByte(1); return encodeContent(command.getDeviceId(), CastelProtocolDecoder.MSG_CC_PETROL_CONTROL, content); case Command.TYPE_ENGINE_RESUME: content.writeByte(0); return encodeContent(command.getDeviceId(), CastelProtocolDecoder.MSG_CC_PETROL_CONTROL, content); default: return null; } } }