Return a pair of socket object and string address.

        May block!

def get_connection(self):
        """
        Return a pair of socket object and string address.

        May block!
        """
        conn = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
        try:
            conn.bind(self._agent._get_filename())
            conn.listen(1)
            (r, addr) = conn.accept()
            return r, addr
        except:
            raise