fr=self._socket.makefile(mode="rb")

		fw=self._socket.makefile(mode="wb")

		self.incoming=NetworkReader(fr)

		self.outcoming=NetworkWriter(fw)

	def __enter__(self):

		return self.incoming,self.outcoming

	def __exit__(self, exc_type, exc_val, exc_tb):

		self._socket.close()

class Server:

	def __init__(self,filename,treeFile=""):

		self._filename=filename

		self._treeFile=treeFile

		if treeFile:

			self._tree=HashTree.load(treeFile)

		else:

			self._tree=HashTree.fromFile(filename)

		self._newLeaves=dict()

		self.BLOCK_SIZE=self._tree.BLOCK_SIZE

		self._ss = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

		self._ss.bind(("", conf.port))

		self._ss.listen(1)

		self._lastWrite=-1

		self._dataFile=None

	def serve(self):

		while True:

			with Connection(self._ss) as (incoming, outcoming):

				try:

					while True:

						if not self._serveOne(incoming,outcoming): return

				except AssertionError:

					continue

	def _serveOne(self,incoming,outcoming):

		jsonData,binData=incoming.readMsg()

		if jsonData["command"]=="init":

			assert jsonData["blockSize"]==self.BLOCK_SIZE

			assert jsonData["blockCount"]==self._tree.leafCount

			outcoming.writeMsg({"command": "ack"})

		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":

			self._finalize()

			return False

		else:

			assert False, jsonData["command"]

		return True

	def _requestHash(self,jsonData):

		log.info("received request for node #{0}".format(jsonData["index"]))

		assert jsonData["index"]<len(self._tree.store)

		nodeHash=self._tree.store[jsonData["index"]]

		jsonResponse={"command":"send", "index":jsonData["index"], "dataType":"hash"}

		binResponse=nodeHash

		return (jsonResponse,binResponse)

	def _receiveData(self,jsonData,binData):

		log.info("received data block #{0}: {1}...{2}".format(jsonData["index"],binData[:5],binData[-5:]))

		if not self._dataFile:

			self._dataFile=open(self._filename, mode="rb+")

		i=jsonData["index"]

		if self._lastWrite+1!=i:

			self._dataFile.seek(i * self.BLOCK_SIZE)

		self._dataFile.write(binData)

		self._lastWrite=i

		if self._treeFile:

			self._newLeaves[i + self._tree.leafStart]= hashlib.sha256(binData).digest()[HashTree.HASH_LEN:]

		return ({"command": "ack", "index": i},)

	def _finalize(self):

		log.info("closing session...")

		if self._dataFile:

			self._dataFile.close()

		if self._treeFile:

			log.info("updating hash tree...")

				self._tree.updateLeaf(k, v)

			self._tree.save(self._treeFile)

		log.info("done")