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/*
* Copyright 2017 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.ChannelHandlerContext;
import io.netty.handler.codec.LineBasedFrameDecoder;
import org.traccar.NetworkMessage;
public class AlematicsFrameDecoder extends LineBasedFrameDecoder {
private static final int MESSAGE_MINIMUM_LENGTH = 2;
public AlematicsFrameDecoder(int maxFrameLength) {
super(maxFrameLength);
}
// example of heartbeat: FA F8 00 07 00 03 15 AD 4E 78 3A D2
@Override
protected Object decode(ChannelHandlerContext ctx, ByteBuf buf) throws Exception {
if (buf.readableBytes() < MESSAGE_MINIMUM_LENGTH) {
return null;
}
if (buf.getUnsignedShort(buf.readerIndex()) == 0xFAF8) {
ByteBuf heartbeat = buf.readRetainedSlice(12);
if (ctx != null && ctx.channel() != null) {
ctx.channel().writeAndFlush(new NetworkMessage(heartbeat, ctx.channel().remoteAddress()));
}
}
return super.decode(ctx, buf);
}
}
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