1 files changed, 72 insertions, 0 deletions
diff --git a/src/main/java/org/traccar/protocol/NavtelecomProtocolDecoder.java b/src/main/java/org/traccar/protocol/NavtelecomProtocolDecoder.java
new file mode 100644
index 000000000..2362b1870
--- /dev/null
+++ b/src/main/java/org/traccar/protocol/NavtelecomProtocolDecoder.java
@@ -0,0 +1,72 @@
+/*
+ * 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);
+    }
+
+    @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 sentence = buf.readCharSequence(length, StandardCharsets.US_ASCII).toString();
+
+        if (sentence.startsWith("*>S")) {
+
+            String data = "*<S";
+
+            ByteBuf response = Unpooled.buffer();
+            response.writeCharSequence("@NTC", StandardCharsets.US_ASCII);
+            response.writeIntLE(sender);
+            response.writeIntLE(receiver);
+            response.writeShortLE(data.length());
+            response.writeByte(Checksum.xor(data));
+            response.writeByte(Checksum.xor(response.nioBuffer()));
+            response.writeCharSequence(data, StandardCharsets.US_ASCII);
+
+            if (channel != null) {
+                channel.writeAndFlush(new NetworkMessage(response, remoteAddress));
+            }
+
+        }
+
+        return null;
+    }
+
+}