Sends the USER message.
        Required arguments:
        * user - Username to send.
        * real_name - Real name to send.

def _user(self, user, real_name):
        """
        Sends the USER message.
        Required arguments:
        * user - Username to send.
        * real_name - Real name to send.
        """
        with self.lock:
            self.send('USER %s 0 * :%s' % (user, real_name))
            if self.readable():
                self._recv()
                self.stepback()