3 files changed, 18 insertions, 9 deletions
diff --git a/src/org/traccar/helper/Checksum.java b/src/org/traccar/helper/Checksum.java
index 43ba6a689..7a0151d36 100644
--- a/src/org/traccar/helper/Checksum.java
+++ b/src/org/traccar/helper/Checksum.java
@@ -243,4 +243,12 @@ public final class Checksum {
         return (10 - (checksum % 10)) % 10;
     }
 
+    public static int modulo256(byte... bytes) {
+        int sum = 0;
+        for (byte b : bytes) {
+            sum = (sum + b) & 0xFF;
+        }
+        return sum;
+    }
+
 }
diff --git a/src/org/traccar/protocol/Arnavi4ProtocolDecoder.java b/src/org/traccar/protocol/Arnavi4ProtocolDecoder.java
index caa8dd28f..46caebb71 100644
--- a/src/org/traccar/protocol/Arnavi4ProtocolDecoder.java
+++ b/src/org/traccar/protocol/Arnavi4ProtocolDecoder.java
@@ -5,6 +5,7 @@ import org.jboss.netty.buffer.ChannelBuffers;
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
 import org.traccar.DeviceSession;
+import org.traccar.helper.Checksum;
 import org.traccar.model.Position;
 
 import java.net.SocketAddress;
@@ -35,14 +36,6 @@ public class Arnavi4ProtocolDecoder extends BaseProtocolDecoder {
         super(protocol);
     }
 
-    private static int modulo256Checksum(byte[] bytes) {
-        int sum = 0;
-        for (byte b : bytes) {
-            sum = (sum + b) & 0xFF;
-        }
-        return sum;
-    }
-
     private Position decodePosition(DeviceSession deviceSession, ChannelBuffer buf, long timestamp) {
 
         final Position position = new Position();
@@ -107,7 +100,7 @@ public class Arnavi4ProtocolDecoder extends BaseProtocolDecoder {
                     response = ChannelBuffers.dynamicBuffer(ByteOrder.LITTLE_ENDIAN, 9);
                     response.writeBytes(new byte[]{0x7B, 0x04, 0x00});
                     byte[] timestampBytes = ByteBuffer.allocate(4).putInt((int) (System.currentTimeMillis() / 1000)).array();
-                    response.writeByte(modulo256Checksum(timestampBytes));
+                    response.writeByte(Checksum.modulo256(timestampBytes));
                     response.writeBytes(timestampBytes);
                     response.writeByte(0x7D);
 
diff --git a/test/org/traccar/helper/ChecksumTest.java b/test/org/traccar/helper/ChecksumTest.java
index c37eda88d..737b65c62 100644
--- a/test/org/traccar/helper/ChecksumTest.java
+++ b/test/org/traccar/helper/ChecksumTest.java
@@ -4,6 +4,7 @@ import org.jboss.netty.buffer.ChannelBuffer;
 import org.jboss.netty.buffer.ChannelBuffers;
 import org.junit.Assert;
 import org.junit.Test;
+import org.traccar.protocol.Arnavi4ProtocolDecoder;
 
 import java.nio.charset.StandardCharsets;
 
@@ -28,4 +29,11 @@ public class ChecksumTest {
         Assert.assertEquals(0, Checksum.luhn(63070019470771L));
     }
 
+    @Test
+    public void testModulo256() {
+        Assert.assertEquals(0x00, Checksum.modulo256((byte)0x00));
+        Assert.assertEquals(0x00, Checksum.modulo256((byte)0x00, (byte)0x00, (byte)0x00));
+        Assert.assertEquals(0x06, Checksum.modulo256((byte)0x01, (byte)0x02, (byte)0x03));
+    }
+
 }