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 org.traccar.BaseProtocolEncoder; import org.traccar.helper.Checksum; import org.traccar.model.Command; import io.netty.buffer.ByteBuf; import io.netty.buffer.Unpooled; import java.nio.charset.StandardCharsets; public class TeltonikaProtocolEncoder extends BaseProtocolEncoder { private ByteBuf encodeContent(String content) { ByteBuf buf = Unpooled.buffer(); buf.writeInt(0); buf.writeInt(content.length() + 10); buf.writeByte(TeltonikaProtocolDecoder.CODEC_12); buf.writeByte(1); // quantity buf.writeByte(5); // type buf.writeInt(content.length() + 2); buf.writeBytes(content.getBytes(StandardCharsets.US_ASCII)); buf.writeByte('\r'); buf.writeByte('\n'); buf.writeByte(1); // quantity buf.writeInt(Checksum.crc16(Checksum.CRC16_IBM, buf.nioBuffer(8, buf.writerIndex() - 8))); return buf; } @Override protected Object encodeCommand(Command command) { switch (command.getType()) { case Command.TYPE_CUSTOM: return encodeContent(command.getString(Command.KEY_DATA)); default: return null; } } }