node.js做app store支付收据的二次验证

  var postdata =
    {
        method: 'POST',
        uri: 'https://sandbox.itunes.apple.com/verifyReceipt',
        multipart:
            [
                { 'content-type': 'text/plain; charset=ISO-8859-1',
                    'body': "{\"receipt-data\":\""+reciept+"\"}"
                }
            ]
    };
    request(postdata, function (error, response, body) {
        if (!error && response.statusCode == 200) {
            console.log("bodytostring---"+JSON.stringify(body));
            console.log("body---"+body);

            callback1(JSON.parse(body));
        }
    });
但是总是返回21002.有哪位大神指点下