From ca8397232467ca70db44b3b3b089409f7e9ee21a Mon Sep 17 00:00:00 2001
From: Anton Tananaev <anton.tananaev@gmail.com>
Date: Thu, 12 Jan 2017 02:37:54 +1300
Subject: Avoid sending duplicate acks

---
 src/org/traccar/protocol/At2000FrameDecoder.java | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/src/org/traccar/protocol/At2000FrameDecoder.java b/src/org/traccar/protocol/At2000FrameDecoder.java
index 4c849afb7..f87dc3885 100644
--- a/src/org/traccar/protocol/At2000FrameDecoder.java
+++ b/src/org/traccar/protocol/At2000FrameDecoder.java
@@ -30,6 +30,9 @@ public class At2000FrameDecoder extends FrameDecoder {
 
     private boolean firstPacket = true;
 
+    private ChannelBuffer currentBuffer;
+    private int acknowledgedBytes;
+
     private void sendResponse(Channel channel) {
         if (channel != null) {
             ChannelBuffer response = ChannelBuffers.directBuffer(ByteOrder.LITTLE_ENDIAN, 2 * BLOCK_LENGTH);
@@ -63,7 +66,11 @@ public class At2000FrameDecoder extends FrameDecoder {
         }
 
         if (buf.readableBytes() >= length || buf.readableBytes() % ACK_LENGTH == 0) {
-            sendResponse(channel);
+            if (buf != currentBuffer || buf.readableBytes() > acknowledgedBytes) {
+                sendResponse(channel);
+                currentBuffer = buf;
+                acknowledgedBytes = buf.readableBytes();
+            }
         }
 
         if (buf.readableBytes() >= length) {
-- 
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