restructuring for project (Backlog 3)

Java/ProjectModels/CognitiveModel/XPCdependencies/BeaconParser.java

@@ -0,0 +1,54 @@
+package ProjectModels.CognitiveModel.XPCdependencies;
+
+import java.io.IOException;
+import java.net.DatagramPacket;
+import java.net.InetAddress;
+import java.nio.ByteBuffer;
+import java.nio.ByteOrder;
+
+/**
+ * Parser class that parses the UDP discovery BECN packet. The format of the packet is
+ * - 4 bytes: BECN
+ * - 1 byte: 0
+ * - 2 bytes: XPlaneConnect server port e.g. '49009'
+ * - 4 bytes: X-Plane version e.g. '11260'
+ * - null terminated string: XPlaneConnect plugin version e.g. '1.3-rc.1'
+ */
+public class BeaconParser {
+
+    private static String BECN = "BECN";
+
+    private static int XPC_PORT_OFFSET = BECN.length() + 1;
+    private static int XPC_PORT_LEN = 2;
+    private static int XPC_VERSION_OFFSET = XPC_PORT_OFFSET + XPC_PORT_LEN;
+    private static int XPC_VERSION_LEN = 4;
+    private static int XPC_PLUGIN_VERSION_OFFSET = XPC_VERSION_OFFSET + XPC_VERSION_LEN;
+
+
+    public Beacon readBCN(DatagramPacket packet) throws IOException {
+        if (packet.getLength() < BECN.length()) {
+            throw new IOException("BECN response too short");
+        }
+
+        byte[] data = packet.getData();
+
+        String command = new String(data, 0, BECN.length());
+        if (!command.equals(BECN)) {
+            throw new IOException("Expected " + BECN + " got '" + command + "'");
+        }
+
+        InetAddress address = packet.getAddress();
+        ByteBuffer bb = ByteBuffer.wrap(data);
+        bb.order(ByteOrder.LITTLE_ENDIAN);
+        // 2 bytes: port as short + converted to an int
+        int port = bb.getShort(XPC_PORT_OFFSET) & 0xffff;
+
+        // 4 bytes: x plane version as int
+        int version = bb.getInt(XPC_VERSION_OFFSET);
+
+        // plugin version
+        String pluginVersion = new String(data, XPC_PLUGIN_VERSION_OFFSET, packet.getLength() - XPC_PLUGIN_VERSION_OFFSET);
+
+        return new Beacon(address, port, pluginVersion.trim(), version);
+    }
+}