diff --git a/src/client.py b/src/client.py
--- a/src/client.py
+++ b/src/client.py
@@ -59,24 +59,30 @@ class Client:
 		print(datetime.now(), "negotiating:")
 		progress=Progress(localTree.leafCount)
 		while len(nodeStack)>0:
-			i=nodeStack.pop()
-			self._outcoming.writeMsg({"command":"req", "index":i, "dataType":"hash"})
+			indices=[]
+			for i in range(256):
+				indices.append(nodeStack.pop())
+				if len(nodeStack)==0: break
+			indices.sort()
+			self._outcoming.writeMsg({"command":"req", "index":indices, "dataType":"hash"})
 
 			jsonData,binData=self._incoming.readMsg()
-			assert jsonData["index"]==i
+			assert jsonData["index"]==indices
 			assert jsonData["dataType"]=="hash"
-			stats.logExchangedNode()
+			stats.logExchangedNode(len(indices))
 
-			if localTree.store[i]!=binData:
-				if 2*i+3<len(localTree.store): # inner node
-					nodeStack.append(2*i+2)
-					nodeStack.append(2*i+1)
-				else:
-					blocksToTransfer.append(i-localTree.leafStart) # leaf
-					progress.p(i-localTree.leafStart)
+			for (j,i) in enumerate(indices):
+				(j1,j2)=[HashTree.HASH_LEN*ji for ji in (j,j+1)]
+				if localTree.store[i]!=binData[j1:j2]:
+					if 2*i+3<len(localTree.store): # inner node
+						nodeStack.append(2*i+2)
+						nodeStack.append(2*i+1)
+					else:
+						blocksToTransfer.append(i-localTree.leafStart) # leaf
+						progress.p(i-localTree.leafStart)
 		progress.done()
 
-		return blocksToTransfer
+		return sorted(blocksToTransfer)
 
 	def sendData(self,blocksToTransfer):
 		log.info(blocksToTransfer)