Listen for controllers.

def run(self):
        """
        Listen for controllers.
        """
        while True:
            data, sender = self.sock.recvfrom(1024)
            addr = sender[0]
            msg = data.decode('utf-8')
            if msg.startswith('/controller/'):
                try:
                    uid = msg.split('/')[2]
                    if uid == 'new':
                        port = int(msg.split('/')[3])
                        self._new_controller(addr, port)
                    else:
                        cmd = msg.split('/')[3]
                        if cmd == 'ping':
                            port = msg.split('/')[3]
                            self._ping(uid, addr, port)
                        elif cmd == 'kthxbye':
                            self._del_controller(uid)
                        elif cmd == 'states':
                            states = msg.split('/')[4]
                            self._update_states(uid, states)
                        elif cmd == 'text':
                            # /controller/<uid>/text/<text>
                            text = msg[12 + len(uid) + 6:]
                            self._got_message(uid, text)
                except IndexError or KeyError:
                    pass
            else:
                pass

            # find unused controllers and delete them
            ctlrs = self.controllers.items()
            for uid, state in ctlrs:
                if state[3] < time.time() - 60:
                    self.controllers.pop(uid)