Create Loop Script for a function

I'm pretty much a beginner in Python. I'm having a project to create a UDP chat in Python. I want to resolve an issue of creating an Online message. I typed the code but it is giving error.

#! /usr/bin/env python
#coding:utf-8

from twisted.internet.task import LoopingCall
from twisted.internet import reactor
from twisted.internet.protocol import DatagramProtocol

def mensagem_presenca():
    print("Estou Online!!")

class Client(DatagramProtocol):
    def sendMessage(self, data, host, port):
        self.transport.write(data, host, port)


lc = LoopingCall(sendMessage("teste", localhost, 8888))
lc.start(30.0)


reactor.run()

  

luiz @ luiz: ~ $ python teste_timer.py Traceback (most recent call last):   File "test_timer.py", line 16, in       lc = LoopingCall (sendMessage ("test", localhost, 8888)) NameError: name 'sendMessage' is not defined luiz @ luiz: ~ $

What can it be?