Fix ConnectionResetError issues and switch to aiohttp version 3.4.4. Fixes #1474.

gns3server/web/route.py

@@ -221,6 +221,7 @@ class Route(object):
                     response = Response(request=request, route=route)
                     response.set_status(408)
                     response.json({"message": "Request canceled", "status": 408})
+                    raise  # must raise to let aiohttp know the connection has been closed
                 except aiohttp.ClientError:
                     log.warning("Client error")
                     response = Response(request=request, route=route)

gns3server/web/web_server.py

@@ -102,7 +102,10 @@ class WebServer:
             return
 
         # close websocket connections
-        for ws in set(self._app['websockets']):
+        websocket_connections = set(self._app['websockets'])
+        if websocket_connections:
+            log.info("Closing {} websocket connections...".format(len(websocket_connections)))
+        for ws in websocket_connections:
             await ws.close(code=aiohttp.WSCloseCode.GOING_AWAY, message='Server shutdown')
 
         if self._server: