WMSLayer display perfectly in arccatalog and arcmap but in flex

DamonSong

Hi,
    I publish a map service with WMS capability, it displays perfectly when added to arcmap and previews in arccatalog, but shows nothing in flex project using WMSLayer, the arcgis api for flex is 2.2. Any suggestions?
    thanks in advance for any help!
following is my code.

<?xml version="1.0" encoding="utf-8"?>
<s:Application xmlns:fx="http://ns.adobe.com/mxml/2009"
      xmlns:s="library://ns.adobe.com/flex/spark"
      xmlns:esri="http://www.esri.com/2008/ags">
 <fx:Script>
  <![CDATA[
   import com.esri.ags.Units;
  ]]>
 </fx:Script>
 <esri:Map units="{Units.DECIMAL_DEGREES}">
  <esri:WMSLayer 
   url="http://sdm:8399/arcgis/services/nef/MapServer/WMSServer"/>
 </esri:Map>
</s:Application>

DasaPaddock

Are you accessing your Flex app at http://sdm:8399/...? If not, you'll need a crossdomain.xml file at http://sdm:8399/crossdomain.xml

See References book at:
http://help.arcgis.com/en/webapi/flex/help/index.html