Uploadpng problem(use asp)

Unity Engine
1

Hi! evryone!
My cody is run nice but the uploaded png is black and size is only 3bytes.
I want to know what difference between webpage form and wwwform when uploadfile! Thanks!

screen.js

var screenShotURL= "http://****/screenshot.asp";

// Take a screen shot immediately
function Start()
{
	print("uping...");
	UploadPNG();
}
function UploadPNG()
{
// We should only read the screen after all rendering is complete
yield WaitForEndOfFrame();
 var width = Screen.width;
var height = Screen.height;
(Screen.width, Screen.height, 24); 
// Create a texture the size of the screen, RGB24 format

var tex = new Texture2D( width, height, TextureFormat.RGB24, false );

// Read screen contents into the texture
tex.ReadPixels( Rect(0, 0, width, height), 0, 0 );
tex.Apply();

// Encode texture into PNG
var bytes = tex.EncodeToPNG();
Destroy( tex );
//File.WriteAllBytes(Application.dataPath + "/../Temp/SavedScreen.png", bytes);

// Create a Web Form
var form = new WWWForm();
//form.AddField("filepath", "screenshot_img");
form.AddBinaryData("fileUpload", bytes, "screenShot.png", "image/png");

// Upload to a cgi script 
var w = WWW(screenShotURL, form);
yield w;
if (w.error != null)
{
	print(w.error); 
}
else
{
	print(w.data); 
}
}

screenshot.asp

<%

		dim filePath:filePath=server.MapPath("/")"\screenshot_img/" ' save path 
		dim lf:lf=chrB(13)&chrB(10)  
         
		dim hct:hct=request.ServerVariables("CONTENT_TYPE") ' the file type 
            'response.write "request.ServerVariables("CONTENT_TYPE"): " 
            'response.write hct 
		dim bTotal ' bytes size 
            bTotal=cLng(request.TotalBytes) 
            'response.write bTotal 
        dim bRead  
            bRead=request.BinaryRead(bTotal) 
		dim bStart:bStart=instrB(bRead,lf&lf)+3 ' start pos
			'response.Write bStart
		dim cTy:cTy=binToStr(midB(bRead,1,bStart-1)) ' Field head info
			'response.Write cTy
		dim fieldMarker '  Field marker
            fieldMarker=leftB(bRead,inStrB(bRead,chrB(13))-1) 
             
        dim cDesc '  Field desc info 
            cDesc=fRegExpSgl(cTy,true,true,true,"[\s\S]*?Content-Disposition\: (.*?)\;[\s\S]*","$1") 
             
        dim fldName ' Field name
            fldName=fRegExpSgl(cTy,true,true,true,"[\s\S]*?name\=\""(.*?)""[\s\S]*","$1") 
         	'response.Write fldName
        dim fileName 
            fileName=fRegExpSgl(cTy,true,true,true,"[\s\S]*filename\=""(.*?)""[\s\S]*","$1") 
            'response.Write fileName
        dim cTp 'MIME type desc
            cTp=fRegExpSgl(cTy,true,true,true,"[\s\S]*?Content-Type\:(.*?)","$1") 
            'response.Write cTp
        dim bEnd ' end pos 
            bEnd=inStrB(bStart+6,bRead,fieldMarker)-bStart-3 
		''''''''''''''''''''''''''''''''''''''''''''''''''''''
		''''''''''''''''''''''''''''''''''''''''''''''''''''''	
		dim stm  
        set stm=createObject("adodb.stream") 
            stm.type=1 
            stm.mode=3 ' read and write mode
            stm.open 
            stm.write bRead 
         
            dim fromStm 
            set fromStm=createOBject("adodb.stream") 
                with fromStm 
                    .type=1 
                    .mode=3 
                    .open 
                    stm.position = bStart 
                    stm.copyTo fromStm, bEnd 
                    .saveTofile filePath&fileName,2 ' save file overwrite mode 
                    .close 
                end with 
            set fromStm=nothing 
     
            stm.close 
        set stm=nothing 
		response.Write("update ok")
		''''''''''''''''''''''
		''''''''''''''''''''''
		function fRegExpSgl(str,glb,igc,mtl,pt,rpt) 
            dim re 
            set re=new RegExp 
                re.global=glb 
                re.ignoreCase=igc 
                re.multiline=mtl 
                 
                re.pattern=pt 
                fRegExpSgl=re.replace(str,rpt) 
            set re=nothing 
        end function

		private function binToStr(bin) 'bytes to  string (bmp|gif|png|jpg) 
        
            dim i, iByt, sByt, bLen:bLen=lenB(bin) 
            for i=1 to bLen 
                sByt=midB(bin,i,1):iByt=ascB(sByt) 
                if iByt<128 then 
                    binToStr=binToStr&chr(iByt) 
                else:i=i+1 
                    if i<=bLen then binToStr=binToStr&chr(ascW(sByt&sByt)) 
                end if 
            next  
        end function 
%>
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