54 lines
1.8 KiB
Java
54 lines
1.8 KiB
Java
package CognitiveModel.ModelFiles.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);
|
|
}
|
|
} |