Invalid grant issue with Google OAuth authentication in Qt

  • I'm developing a Qt application and I want to use Google authentication for it. I created a Google API as explained in the following link: but I have a problem with it. It doesn't work in many cases and I get ProtocolInvalidOperationError(302) error for request URL in
    QOAuthHttpServerReplyHandler::networkReplyFinished(QNetworkReply *reply)
    method of Qt class.

    Note that I override QOAuthHttpServerReplyHandler::networkReplyFinished(QNetworkReply *reply) to get this error, because it doesn't emit any signal in this case, and the return value for reply->readAll() is as below:

      "error": "invalid_grant",
      "error_description": "Malformed auth code."

    My Login.cpp code is something as below:

    Login::Login() {
        google = new QOAuth2AuthorizationCodeFlow;
        connect(google, &QOAuth2AuthorizationCodeFlow::authorizeWithBrowser,
        connect(google,&QOAuth2AuthorizationCodeFlow::authorizationCallbackReceived,[=](const QVariantMap data){
        QString code(data["code"].toString());
            const QUrl redirectUri= "http://localhost:56413/cb";
            QJsonObject postdata;
            postdata.insert("client_id", Utility::decrypt(encryptedClientId));
            postdata.insert("client_secret", Utility::decrypt(encryptedClientSecret));
            postdata.insert("redirect_uri", redirectUri.toString());
           QString serviceURL = "oauth2/v4/token";
           NetworkManager::GetInstance()->Post(postdata,serviceURL,"",[=](int statusCode,int resultnumber, QJsonObject obj){
    		   if (statusCode >= 200 &&   statusCode < 300) {
    			   // it's ok, do nothing
    		   else {
                   //show error
    void Login::googleLoginButtonPressed() {
        int googlePort = 56413;
        if(replyHandler == nullptr)
    	replyHandler = new QOAuthHttpServerReplyHandlerArio(googlePort, this);
        QObject::connect(replyHandler, &QOAuthHttpServerReplyHandler::tokensReceived, [=](const QVariantMap &map) {
    	googleToken = map["id_token"].toString();
    	connect(google, &QOAuth2AuthorizationCodeFlow::granted, [=]() {
    		auto reply = google->get(QUrl(""));
    		connect_reply = connect(reply, &QNetworkReply::finished, [=]() {
    			int statusCode = reply->attribute(QNetworkRequest::HttpStatusCodeAttribute).toInt();
    			if (statusCode >= 200 &&
    				statusCode < 300)
    				//NOW register or login the user with email
    				QJsonDocument jsonResponse = QJsonDocument::fromJson(reply->readAll().data());
    				email = jsonResponse.object().value("emails").toArray()[0].toObject().value("value").toString();
    			else {

    Also my Qt version is 5.9.1.
    what's the problem?

    Thanks for your help.

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