def is_ipv4_address(addr):
    """
    Determine whether the given string represents an IPv4 address.
    Code from twisted project.
    """
    dottedParts = addr.split('.')
    if len(dottedParts) == 4:
        for octet in dottedParts:
            try:
                value = int(octet)
            except ValueError:
                return False
            else:
                if value < 0 or value > 255:
                    return False
        return True
    return False