Publish to Node-RED on Digital Ocean (MicroPython)

main.py

import time
from umqttsimple import MQTTClient
import ubinascii
import machine
import micropython
import network
import esp
from machine import Pin
#import onewire
#import ds18x20
esp.osdebug(None)
import gc
gc.collect()

ssid = 'REPLACE_WITH_YOUR_SSID'
password = 'REPLACE_WITH_YOUR_PASSWORD'
#EXAMPLE IP ADDRESS
#add your mqtt server below
mqtt_server = '178.62.83.XXX'

client_id = ubinascii.hexlify(machine.unique_id())

topic_pub_temp = b'esp/ds18b20/temperature'

last_message = 0
message_interval = 5

station = network.WLAN(network.STA_IF)

station.active(True)
station.connect(ssid, password)

while station.isconnected() == False:
  pass

print('Connection successful')

#ds_pin = machine.Pin(4)
#ds_sensor = ds18x20.DS18X20(onewire.OneWire(ds_pin))

def connect_mqtt():
  global client_id, mqtt_server
  client = MQTTClient(client_id, mqtt_server, user='your_user', password='your_pass')
  client.connect()
  print('Connected to %s MQTT broker' % (mqtt_server))
  return client

def restart_and_reconnect():
  print('Failed to connect to MQTT broker. Reconnecting...')
  time.sleep(10)
  machine.reset()

def read_sensor():
  #try:
  #  roms = ds_sensor.scan()
  #  ds_sensor.convert_temp()
  #  time.sleep_ms(750)
  #  for rom in roms: 
  #    temp = ds_sensor.read_temp(rom)
  #    # uncomment for Fahrenheit
  #    temp = temp * (9/5) + 32.0
  #  if (isinstance(temp, float) or (isinstance(temp, int))):
  #    temp = (b'{0:3.1f},'.format(temp))
  #    return temp
  #  else:
  #    return('Invalid sensor readings.')
  #except OSError as e:
  #  return('Failed to read sensor.')
  return b'5'

try:
  client = connect_mqtt()
except OSError as e:
  restart_and_reconnect()

while True:
  try:
    if (time.time() - last_message) > message_interval:
      temp = read_sensor()
      print(temp)
      client.publish(topic_pub_temp, temp)
      last_message = time.time()
  except OSError as e:
    restart_and_reconnect()