diff --git a/oml/nodes.py b/oml/nodes.py
index d16b402..ea89cf7 100644
--- a/oml/nodes.py
+++ b/oml/nodes.py
@@ -542,6 +542,8 @@ class Nodes(Thread):
             self.queue('pull')
 
     def _pull(self):
+        if not state.sync_enabled or settings.preferences.get('downloadRate') == 0:
+            return
         if state.activity and state.activity.get('activity') == 'import':
             return
         self._pulling = True
diff --git a/oml/server.py b/oml/server.py
index 89401d0..d0e997d 100644
--- a/oml/server.py
+++ b/oml/server.py
@@ -6,7 +6,6 @@ import sys
 import signal
 import time
 
-from tornado.httpserver import HTTPServer
 from tornado.ioloop import IOLoop
 from tornado.web import StaticFileHandler, Application
 
@@ -71,7 +70,6 @@ def shutdown():
         logger.debug('shutdown downloads')
         state.downloads.join()
     logger.debug('shutdown http_server')
-    state.http_server.stop()
     if state.tasks:
         logger.debug('shutdown tasks')
         state.tasks.join()
@@ -135,8 +133,9 @@ def run():
     ]
 
     setup.create_db()
-    http_server = HTTPServer(Application(handlers, **options))
-    http_server.listen(settings.server['port'], settings.server['address'])
+    http_server = Application(handlers, **options)
+    max_buffer_size = 2*1024*1024*1024
+    http_server.listen(settings.server['port'], settings.server['address'], max_buffer_size=max_buffer_size)
 
     if PID:
         with open(PID, 'w') as pid:
diff --git a/oml/state.py b/oml/state.py
index 7f63690..4768e7b 100644
--- a/oml/state.py
+++ b/oml/state.py
@@ -8,6 +8,7 @@ node = False
 online = False
 tasks = False
 downloads = False
+sync_enabled = True
 tor = False
 update = False
 shutdown = False
diff --git a/oml/update.py b/oml/update.py
index c265f63..566d66b 100644
--- a/oml/update.py
+++ b/oml/update.py
@@ -333,7 +333,9 @@ class Update(Thread):
     def install(self):
         while update_available():
             self.status('Downloading...')
-            while not download():
+            max_retry = 5
+            while max_retry > 0 and not download():
+                max_retry -= 1
                 self.status('Download failed, retrying...')
                 time.sleep(5)
                 self.status('Downloading...')
diff --git a/oml/websocket.py b/oml/websocket.py
index 466adeb..7e468f2 100644
--- a/oml/websocket.py
+++ b/oml/websocket.py
@@ -57,11 +57,10 @@ class Handler(WebSocketHandler):
 
     def post(self, event, data):
         message = json_dumps([event, data])
-        main = IOLoop.instance()
         if self.ws_connection is None:
             self.on_close()
         else:
-            main.add_callback(lambda: self.write_message(message))
+            state.main.add_callback(lambda: self.write_message(message))
 
 def trigger_event(event, data):
     #if len(state.websockets):
diff --git a/requirements-shared.txt b/requirements-shared.txt
index 934cfb4..2edce59 100644
--- a/requirements-shared.txt
+++ b/requirements-shared.txt
@@ -1,5 +1,5 @@
-requests==2.9.1
-tornado==4.3
+requests==2.21.0
+tornado==5.1.1
 chardet
 html5lib
 #ox>=2.0.666
@@ -8,5 +8,5 @@ python-stdnum==1.2
 PyPDF2==1.25.1
 pysocks
 stem
-sqlitedict==1.4.0
+sqlitedict==1.6.0
 zeroconf