From e9d77d16a99874ef4c5eb44dc15994811d724b9d Mon Sep 17 00:00:00 2001
From: Evgeny S Maksimov <admin@vragam.net>
Date: Tue, 29 Jan 2019 19:55:31 +0300
Subject: Support for downgrading the FLEX protocol version

---
 src/org/traccar/protocol/NavisProtocolDecoder.java | 32 ++++++++++++----------
 1 file changed, 17 insertions(+), 15 deletions(-)

(limited to 'src/org/traccar')

diff --git a/src/org/traccar/protocol/NavisProtocolDecoder.java b/src/org/traccar/protocol/NavisProtocolDecoder.java
index 0bebfe0d2..f6fa75c58 100644
--- a/src/org/traccar/protocol/NavisProtocolDecoder.java
+++ b/src/org/traccar/protocol/NavisProtocolDecoder.java
@@ -588,24 +588,26 @@ public class NavisProtocolDecoder extends BaseProtocolDecoder {
 
         flexProtocolVersion = (byte) buf.readUnsignedByte();
         flexStructVersion = (byte) buf.readUnsignedByte();
-        if (flexProtocolVersion != (byte) 0x0A && flexProtocolVersion != (byte) 0x14) {
-            return null;
-        }
-        if (flexStructVersion != (byte) 0x0A && flexStructVersion != (byte) 0x14) {
-            return null;
-        }
+        if ((flexProtocolVersion == (byte) 0x0A ||  flexProtocolVersion == (byte) 0x14)
+            && (flexStructVersion == (byte) 0x0A || flexStructVersion == (byte) 0x14)) {
 
-        flexBitfieldDataSize = buf.readUnsignedByte();
-        if (flexBitfieldDataSize > 122) {
-            return null;
-        }
-        buf.readBytes(flexBitfield, 0, (int) Math.ceil((double) flexBitfieldDataSize / 8));
+            flexBitfieldDataSize = buf.readUnsignedByte();
+            if (flexBitfieldDataSize > 122) {
+                return null;
+            }
 
-        flexDataSize = 0;
-        for (int i = 0; i < flexBitfieldDataSize; i++) {
-            if (checkFlexBitfield(i)) {
-                flexDataSize += FLEX_FIELDS_SIZES[i];
+            buf.readBytes(flexBitfield, 0, (int) Math.ceil((double) flexBitfieldDataSize / 8));
+
+            flexDataSize = 0;
+            for (int i = 0; i < flexBitfieldDataSize; i++) {
+                if (checkFlexBitfield(i)) {
+                    flexDataSize += FLEX_FIELDS_SIZES[i];
+                }
             }
+        } else {
+            // Prepare request for downgrade of protocol version to FLEX 2.0
+            flexProtocolVersion = 0x14;
+            flexStructVersion = 0x14;
         }
 
         ByteBuf response = Unpooled.buffer(9);
-- 
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