Connect to the IPC socket

def connect(self, callback=None, timeout=None):
        '''
        Connect to the IPC socket
        '''
        if hasattr(self, '_connecting_future') and not self._connecting_future.done():  # pylint: disable=E0203
            future = self._connecting_future  # pylint: disable=E0203
        else:
            if hasattr(self, '_connecting_future'):
                # read previous future result to prevent the "unhandled future exception" error
                self._connecting_future.exception()  # pylint: disable=E0203
            future = tornado.concurrent.Future()
            self._connecting_future = future
            self._connect(timeout=timeout)

        if callback is not None:
            def handle_future(future):
                response = future.result()
                self.io_loop.add_callback(callback, response)
            future.add_done_callback(handle_future)

        return future