diff --git a/src/client.py b/src/client.py
--- a/src/client.py
+++ b/src/client.py
@@ -4,7 +4,7 @@ import logging as log
 from datetime import datetime
 
 import config as conf
-from util import progress
+from util import Progress
 from hashtree import HashTree
 from networkers import NetworkReader,NetworkWriter
 
@@ -45,6 +45,7 @@ class Client:
 
 			# determine which blocks to send
 			print(datetime.now(), "negotiating:")
+			progress=Progress(localTree.leafCount)
 			while len(nodeStack)>0:
 				i=nodeStack.pop()
 				outcoming.writeMsg({"command":"req", "index":i})
@@ -59,8 +60,8 @@ class Client:
 						nodeStack.append(2*i+1)
 					else:
 						blocksToTransfer.append(i-localTree.leafStart) # leaf
-						progress(i-localTree.leafStart, localTree.leafCount)
-		print("100%")
+						progress.p(i-localTree.leafStart)
+		progress.done()
 
 		return blocksToTransfer
 
@@ -71,6 +72,7 @@ class Client:
 
 		print(datetime.now(), "sending data:")
 		with Connection() as (incoming,outcoming):
+			progress=Progress(len(blocksToTransfer))
 			for (k,i2) in enumerate(blocksToTransfer):
 				jsonData={"command":"send", "index":i2, "dataType":"data"}
 				if i1+1!=i2:
@@ -83,8 +85,8 @@ class Client:
 				jsonData,binData=incoming.readMsg()
 				assert jsonData["command"]=="ack" and jsonData["index"]==i2, jsonData
 				i1=i2
-				progress(k,len(blocksToTransfer))
-		print("100%")
+				progress.p(k)
+		progress.done()
 
 		with Connection() as (incoming,outcoming):
 			outcoming.writeMsg({"command":"end"})
diff --git a/src/hashtree.py b/src/hashtree.py
--- a/src/hashtree.py
+++ b/src/hashtree.py
@@ -2,7 +2,7 @@
 import os
 from datetime import datetime
 
-from util import progress
+from util import Progress
 
 
 class HashTree:
@@ -25,12 +25,13 @@ class HashTree:
 			res=cls(leafCount)
 			print(datetime.now(), "hashing file:")
 
+			progress=Progress(leafCount)
 			for i in range(leafCount):
 				data=f.read(HashTree.BLOCK_SIZE)
 				res.insertLeaf(hashlib.sha256(data).digest()[HashTree.HASH_LEN:])
 
-				progress(i, leafCount)
-			print("100%")
+				progress.p(i)
+			progress.done()
 		res.buildTree()
 		
 		return res
@@ -76,10 +77,11 @@ class HashTree:
 	## Fast construction of the tree over the leaves. O(n).
 	def buildTree(self):
 		print(datetime.now(), "building tree:")
+		progress=Progress(-1, self.leafStart-1)
 		for i in range(self.leafStart-1,-1,-1):
 			self.store[i]=hashlib.sha256(self.store[i*2+1]+self.store[i*2+2]).digest()[HashTree.HASH_LEN:]
-			progress(i, -1, self.leafStart - 1)
-		print()
+			progress.p(i)
+		progress.done()
 
 
 if __name__=="__main__":
diff --git a/src/util.py b/src/util.py
--- a/src/util.py
+++ b/src/util.py
@@ -1,11 +1,25 @@
-def progress(i, n, i0=0):
-	def _progress(i,n,i0):
-		return 100*(i+1-i0)//(n-i0)
+class Progress:
+	def __init__(self,n,i0=0):
+		self._n=n
+		self._i0=i0
+		self._i=i0
+		self._last=""
+
+	def p(self,i):
+		i0=self._i0
+		n=self._n
 
-	if n<i0:
-		i*=-1
-		n*=-1
-		i0*=-1
-	assert i0<=i<n, (i0,i,n)
-	percentage=_progress(i,n,i0)
-	print("{0}%".format(percentage),end="\r")
+		assert i0<=i<n or n<i<=i0, (i0,i,n)
+		percentage=Progress._p(i,n,i0)
+		res="{0}%".format(percentage)
+		if res!=self._last:
+			print(res,end="\r")
+			self._last=res
+
+	def done(self):
+		print("100%")
+
+	@staticmethod
+	def _p(i,n,i0):
+		_1=1 if n>=i0 else -1
+		return 100*(i+_1-i0)//(n-i0)