private int index_for(String variable) {
        int index;
        if (variable.equals("username")) {
            index = username_index;
        } else if (variable.equals("server_number")) {
            index = server_number_index;
        } else if (variable.equals("has_data")) {
            index = has_data_index;
        } else {
            index = -1;
        }
        return index;
    }