loader_balance = new QNetworkAccessManager(this);
QNetworkRequest request = QNetworkRequest(QUrl("http://127.0.0.1:19976/json_rpc"));
request.setHeader(QNetworkRequest::ContentTypeHeader, "application/octet-stream");
connect(loader_balance, SIGNAL(finished(QNetworkReply*)),this, SLOT(rpcReply(QNetworkReply*)));
QString dataStr = "{\"jsonrpc\": \"2.0\", \"method\":\"getbalance\"}";
QJsonDocument jsonData = QJsonDocument::fromJson(dataStr.toUtf8());
QByteArray data = jsonData.toJson();
loader_balance->post(request, data);