Java tutorial
/* * Copyright 2013 - 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.channel.Channel; import io.netty.channel.ChannelHandlerContext; import org.traccar.BaseFrameDecoder; public class CellocatorFrameDecoder extends BaseFrameDecoder { private static final int MESSAGE_MINIMUM_LENGTH = 15; @Override protected Object decode(ChannelHandlerContext ctx, Channel channel, ByteBuf buf) throws Exception { if (buf.readableBytes() < MESSAGE_MINIMUM_LENGTH) { return null; } int length = 0; int type = buf.getUnsignedByte(4); switch (type) { case CellocatorProtocolDecoder.MSG_CLIENT_STATUS: length = 70; break; case CellocatorProtocolDecoder.MSG_CLIENT_PROGRAMMING: length = 31; break; case CellocatorProtocolDecoder.MSG_CLIENT_SERIAL_LOG: length = 70; break; case CellocatorProtocolDecoder.MSG_CLIENT_SERIAL: if (buf.readableBytes() >= 19) { length = 19 + buf.getUnsignedShortLE(16); } break; case CellocatorProtocolDecoder.MSG_CLIENT_MODULAR: length = 15 + buf.getUnsignedByte(13); break; default: break; } if (length > 0 && buf.readableBytes() >= length) { return buf.readRetainedSlice(length); } return null; } }