The working code will be
<object id="flowplayer" data="flowplayer-3.2.2.swf" type="application/x-shockwave-flash" width="320" height="240" >
<param name="movie" value="flowplayer-3.2.2.swf">
<param name="allowfullscreen" value="true">
<param name="flashvars" value="config={'clip':{'url':'mymovie.mp4','autoPlay':false}}">
</object>
your url propery value is VideoHandler.ashx. If so then in your local host server http://localhost:6259" should have that ashx file and it should write video stream to Httpresponse object.