import subprocess

def wait_net_service(server, port, timeout=None):
    """ Wait for network service to appear 
        @param timeout: in seconds, if None or 0 wait forever
        @return: True of False, if timeout is None may return only True or
                 throw unhandled network exception
    """
    import socket
    import errno

    s = socket.socket()
    if timeout:
        from time import time as now
        # time module is needed to calc timeout shared between two exceptions
        end = now() + timeout

    while True:
        try:
            if timeout:
                next_timeout = end - now()
                if next_timeout < 0:
                    return False
                else:
                    s.settimeout(next_timeout)
            s.connect((server, port))
        except socket.timeout as err:
            # this exception occurs only if timeout is set
            if timeout:
                return False
        except socket.error as err:
            # catch timeout exception from underlying network library
            # this one is different from socket.timeout
            if type(err.args) != tuple or err[0] != errno.ETIMEDOUT:
                raise
        else:
            s.close()
            return True


def up2date_anyimages():
    cmd = "docker images -q feedati/*".split()
    output = subprocess.check_output(cmd).strip()
    if output:
        return True
    return False