Outgauge Packet - Java

[FireTiger]

Hello,
i'm programming my own Outgauge Tool in Java.
I take the Outgauge UDP Packet and want to get the 4 Speed Bytes (12 - 15). After that i use a bitshifter to convert this 4 bytes into float.

But the float is totally wrong with the values.
Can anybody see my fault?

Here is the code:

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;

/* Data Packet in detail
* Time [0 - 3]
* AutoName [4 - 7]
* Flags [8 - 9]
* Gang [10]
* SpareB [11]
* Speed [12 - 15]
* RPM [16 - 19]
* Turbo [20 - 23]
* EngTemp [24-27]
* Fuel [28 - 31]
* Öldruck [32 - 35]
* ÖlTemp [36 - 39]
* Dashlight [40 - 43]
* ShowLights [44 - 47]
* Throttle [48 - 51]
* Brake [52 - 55]
* Clutch [56 - 59]
* Display1 [60 - 75]
* Display2 [76 - 91]
* ID [92 - 95]
*/

public class client {
private static final int MASK = 0xff;
/**
* @param args
* @throws IOException
*/
public static void main(String[] args) {
DatagramSocket socket = null;
DatagramPacket packet = new DatagramPacket(new byte[92], 92);

try {
socket = new DatagramSocket(9090);
for(;;) {
socket.receive(packet);

byte data[] = packet.getData();
String AutoName = new String();
AutoName += (char)data[4];
AutoName += (char)data[5];
AutoName += (char)data[6];
AutoName += (char)data[7];

int bits = 0;
int i = 12;
for (int shifter = 3; shifter >= 0; shifter--) {
bits |= ((int)data[i] & MASK) << (shifter * 8);
i++;
}
Float Speed = Float.intBitsToFloat(bits);

System.out.print("Car: " + AutoName + " | Gear: " + (int)data[10]);
System.out.print(" | Speed: " + Speed + "| Len: " + data.length + "\n");
}

} catch (IOException e) {
e.printStackTrace();
} finally {
socket.close();
}


}
}
thx

[MadCatX]

I'm not much into low-level bitwise operations, but have you tried doing it like this?


for(int shifter = 0; shifter < 4; shifter++)
{
bits |= ((long)data[i] & MASK) << (shifter * 8);
i++;
}

[FireTiger]

No, because the function Float Speed = Float.intBitsToFloat(bits);
needs as parameter a integer value.
Integer is in Java 4byte and Float 4byte too.

Are the packets right?

[MadCatX]

You were right about using "int" instead of "long", "long" is needed when you convert to a 64 bit long variable. Anyway, following code seems to be getting correct data for me:


public static void main(String[] args) {
byte[] ogBuf= new byte[92];

DatagramSocket sock = null;
DatagramPacket udpPack = new DatagramPacket(ogBuf, 92);

try
{
sock = new DatagramSocket(30000);

while(true)
{
sock.receive(udpPack);

int bits = 0;
int idx = 12;
for(int shiftBy = 0; shiftBy < 4; shiftBy++)
{
bits |= ((int)ogBuf[idx++] & 0xFF) << (shiftBy * 8);
}

float speed = Float.intBitsToFloat(bits);

System.out.println("Current speed: " + speed*3.6f + " km/h");
}
} catch (Exception ex)
{
ex.printStackTrace();
}
}

[FireTiger]

It's run. Thank you :)
I think it was the bitwise operation :)

[Brilwing]

Just use the ByteBuffer: http://download.oracle.com/javase/6/docs/api/java/nio/ByteBuffer.html