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/*
* Copyright 2021 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 io.netty.channel.Channel;
import org.traccar.BaseProtocolDecoder;
import org.traccar.NetworkMessage;
import org.traccar.Protocol;
import org.traccar.helper.Checksum;
import java.net.SocketAddress;
import java.nio.charset.StandardCharsets;
public class NavtelecomProtocolDecoder extends BaseProtocolDecoder {
public NavtelecomProtocolDecoder(Protocol protocol) {
super(protocol);
}
private void sendResponse(
Channel channel, SocketAddress remoteAddress, int receiver, int sender, ByteBuf content) {
if (channel != null) {
ByteBuf response = Unpooled.buffer();
response.writeCharSequence("@NTC", StandardCharsets.US_ASCII);
response.writeIntLE(sender);
response.writeIntLE(receiver);
response.writeShortLE(content.readableBytes());
response.writeByte(Checksum.xor(content.nioBuffer()));
response.writeByte(Checksum.xor(response.nioBuffer()));
response.writeBytes(content);
content.release();
channel.writeAndFlush(new NetworkMessage(response, remoteAddress));
}
}
@Override
protected Object decode(
Channel channel, SocketAddress remoteAddress, Object msg) throws Exception {
ByteBuf buf = (ByteBuf) msg;
buf.skipBytes(4); // preamble
int receiver = buf.readIntLE();
int sender = buf.readIntLE();
int length = buf.readUnsignedShortLE();
buf.readUnsignedByte(); // data checksum
buf.readUnsignedByte(); // header checksum
String type = buf.toString(buf.readerIndex(), 6, StandardCharsets.US_ASCII);
if (type.startsWith("*>S")) {
String sentence = buf.readCharSequence(length, StandardCharsets.US_ASCII).toString();
getDeviceSession(channel, remoteAddress, sentence.substring(4));
ByteBuf payload = Unpooled.copiedBuffer("*<S", StandardCharsets.US_ASCII);
sendResponse(channel, remoteAddress, receiver, sender, payload);
} else if (type.startsWith("*>FLEX")) {
buf.skipBytes(6);
ByteBuf payload = Unpooled.buffer();
payload.writeByte(buf.readUnsignedByte()); // protocol
payload.writeByte(buf.readUnsignedByte()); // protocol version
payload.writeByte(buf.readUnsignedByte()); // struct version
sendResponse(channel, remoteAddress, receiver, sender, payload);
}
return null;
}
}
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