django - How to use the attribute 'url' of ol.source.OSM -

i've deployed local openstreetmap tile server , tried many times show map using openlayers3, failed unfortunately. here's experiment scene. deploy tile server on port 80, , image correctly via http://127.0.0.1:80/osm_tiles/{z}/{x}/{y}.png. besides, place django web on port 8099, , can access web page via http://127.0.0.1:8099/my/page. in template page, wrote this

var layer = new ol.layer.tile({          source: new ol.source.osm({              attributions: [                  ol.source.osm.attribution              ],              url:'//127.0.0.1:80/osm_tiles2/{z}/{x}/{y}.png'                      })      });    var map= new ol.map({          target : 'map_canvas',          loadtileswhileanimating: true,          view: new ol.view({              center:ol.proj.transform([116.391625,39.906813], 'epsg:4326', 'epsg:3857'),              zoom : 12          }),          layers:[layer]      });

the map_canvas shows nothing, can images tile server in firebug.why? me, many thanks!

try adding crossorigin: null source, so:

var layer = new ol.layer.tile({     source: new ol.source.osm({         attributions: [             ol.source.osm.attribution         ],         url:'//127.0.0.1:80/osm_tiles2/{z}/{x}/{y}.png',         crossorigin: null                 }) });