diff --git a/src/server.py b/src/server.py
--- a/src/server.py
+++ b/src/server.py
@@ -42,33 +42,38 @@ class Server:
 		self.dataFile=None
 
 	def serve(self):
-		while self._serveOne():
-			pass
-
-	def _serveOne(self):
-		with Connection(self.ss) as (incoming,outcoming):
-			jsonData,binData=incoming.readMsg()
+		while True:
+			with Connection(self.ss) as (incoming,outcoming):
+				try:
+					while True:
+						if not self._serveOne(incoming,outcoming): return
+				except AssertionError:
+					continue
 
-			if jsonData["command"]=="init":
-				assert jsonData["blockSize"]==self.BLOCK_SIZE
-				assert jsonData["blockCount"]==self.tree.leafCount
+	def _serveOne(self,incoming,outcoming):
+		jsonData,binData=incoming.readMsg()
 
-			elif jsonData["command"]=="req":
-				outcoming.writeMsg(*self._requestHash(jsonData))
+		if jsonData["command"]=="init":
+			assert jsonData["blockSize"]==self.BLOCK_SIZE
+			assert jsonData["blockCount"]==self.tree.leafCount
+			outcoming.writeMsg({"command": "ack"})
 
-			elif jsonData["command"]=="send" and jsonData["dataType"]=="data":
-				self._receiveData(jsonData,binData)
+		elif jsonData["command"]=="req":
+			outcoming.writeMsg(*self._requestHash(jsonData))
+
+		elif jsonData["command"]=="send" and jsonData["dataType"]=="data":
+			outcoming.writeMsg(*self._receiveData(jsonData,binData))
 
-			elif jsonData["command"]=="end":
-				log.info("closing session...")
-				if self.dataFile:
-					self.dataFile.close()
-				return False
+		elif jsonData["command"]=="end":
+			log.info("closing session...")
+			if self.dataFile:
+				self.dataFile.close()
+			return False
 
-			else:
-				assert False, jsonData["command"]
+		else:
+			assert False, jsonData["command"]
 
-			return True
+		return True
 
 	def _requestHash(self,jsonData):
 		log.info("received request for node #{0}".format(jsonData["index"]))
@@ -91,4 +96,5 @@ class Server:
 		self.dataFile.write(binData)
 		self._lastWrite=i
 
+		return ({"command": "ack", "index": i},)
 		# never update the hash tree