diff --git a/src/server.py b/src/server.py
--- a/src/server.py
+++ b/src/server.py
@@ -32,7 +32,7 @@ class Connection:
 		self.socket.close()
 
 
-localTree=HashTree.fromFile(open(filename,mode="rb"))
+localTree=HashTree.fromFile(filename)
 
 ss = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
 ss.bind(("",conf.port))
@@ -53,8 +53,9 @@ while True:
 			assert jsonData["blockSize"]==localTree.BLOCK_SIZE
 			assert jsonData["blockCount"]==localTree.leafCount
 
-		elif jsonData["command"]=="req": # !! index out of range
+		elif jsonData["command"]=="req":
 			log.info("received request for node #{0}".format(jsonData["index"]))
+			assert jsonData["index"]<len(localTree.store)
 			nodeHash=localTree.store[jsonData["index"]]
 
 			jsonResponse={"command":"send", "index":jsonData["index"], "dataType":"hash"}
@@ -62,7 +63,7 @@ while True:
 
 			outcoming.writeMsg(jsonResponse,binResponse)
 
-		elif jsonData["command"]=="send" and jsonData["dataType"]=="data": # needlessly allow hashes and data in mixed order
+		elif jsonData["command"]=="send" and jsonData["dataType"]=="data":
 			log.info("received data block #{0}: {1}...{2}".format(jsonData["index"],binData[:5],binData[-5:]))
 
 			i2=jsonData["index"]
@@ -77,7 +78,7 @@ while True:
 			log.info("closing session...")
 			break
 	
-		else: pass # !! error
+		else:
+			assert False, jsonData["command"]
 
 dataFile.close()
-sys.exit(0)