how to call web api or service json using flash as3

Dear Friends,

Iam creating an app using Air for IOS, Initially iam doing login screen, when I enter username, and password it should communicate with server, check whether the user exist or not. Iam using web api or service and getting response as json. My other team mates gave me the web service its working fine in browser (tested with fiddler software) and giving result as 200. When iam using the same with AS3 its not working and giving error message as "error":"unsupported_grant_type".  Iam

public function checkServerLogin(aThis: MovieClip = null, aFun: String = null, aValues: String = null) {

    spath = "http://1.0.0.165/testproject/token"

   externalObj = aThis

   customEventName = aFun;   

   var urlVariable: URLVariables = new URLVariables();     

   var myRequest: URLRequest = new URLRequest(spath);

   myRequest.method = URLRequestMethod.POST;  

   var splitvalues= aValues.split("~");

   urlVariable.grant_type="password&username=testuser&password=Abcd1234!";

   myRequest.data = urlVariable;  

   loader.dataFormat = URLLoaderDataFormat.TEXT;

   loader.addEventListener(Event.COMPLETE, check_Server_Data);

   loader.addEventListener(HTTPStatusEvent.HTTP_RESPONSE_STATUS,httpResponceStatus)

   loader.addEventListener(IOErrorEvent.IO_ERROR, check_Server_Data_IOError);

   loader.load(myRequest);

  }

private function check_Server_Data(evt: Event) {

   trace("final result is : "+loader.data);

   loader.removeEventListener(Event.COMPLETE, check_Server_Data);

   loader.removeEventListener(IOErrorEvent.IO_ERROR, check_Server_Data_IOError);

   externalObj[customEventName](accessCode+"|"+loader.data) 

  }

Please help me to solve this issue. Thanks in advance....

Thanks and Regards,

Syed Abdul Rahim