def concat_to_address(ip, port):
    """
    ip: str for address to concat, like "127.0.0.1"
    port: str for port, like "2379"

    return: str like "127.0.0.1:2379"
        return None if ip or port is None
    """
    if ip is None or port is None:
        return None
    return ip.strip() + ":" + port.strip()