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 org.traccar.BaseFrameDecoder; import org.traccar.NetworkMessage; import org.traccar.helper.BufferUtil; import io.netty.buffer.ByteBuf; import io.netty.channel.Channel; import io.netty.channel.ChannelHandlerContext; public class WondexFrameDecoder extends BaseFrameDecoder { private static final int KEEP_ALIVE_LENGTH = 8; @Override protected Object decode(ChannelHandlerContext ctx, Channel channel, ByteBuf buf) throws Exception { if (buf.readableBytes() < KEEP_ALIVE_LENGTH) { return null; } if (buf.getUnsignedByte(buf.readerIndex()) == 0xD0) { // Send response ByteBuf frame = buf.readRetainedSlice(KEEP_ALIVE_LENGTH); if (channel != null) { frame.retain(); channel.writeAndFlush(new NetworkMessage(frame, channel.remoteAddress())); } return frame; } else { int index = BufferUtil.indexOf("\r\n", buf); if (index != -1) { ByteBuf frame = buf.readRetainedSlice(index - buf.readerIndex()); buf.skipBytes(2); return frame; } } return null; } }