Check reachability for specified hostname/port.

    It tries to open TCP socket.
    It supports IPv6.
    :param host: hostname or ip address string
    :rtype: str
    :param port: tcp port number
    :rtype: number
    :return: True if host is reachable else false

def is_reachable(host, port=23):
    """Check reachability for specified hostname/port.

    It tries to open TCP socket.
    It supports IPv6.
    :param host: hostname or ip address string
    :rtype: str
    :param port: tcp port number
    :rtype: number
    :return: True if host is reachable else false
    """
    try:
        addresses = socket.getaddrinfo(
            host, port, socket.AF_UNSPEC, socket.SOCK_STREAM
        )
    except socket.gaierror:
        return False

    for family, _, _, _, sockaddr in addresses:
        sock = socket.socket(family, socket.SOCK_STREAM)
        sock.settimeout(5)
        try:
            sock.connect(sockaddr)
        except IOError:
            continue

        sock.shutdown(socket.SHUT_RDWR)
        sock.close()
        # Wait 2 sec for socket to shutdown
        time.sleep(2)
        break
    else:
        return False
    return True