MTTQ Threaded receive

[crankshaft]

Hi, not sure if this is related to micropython or is a problem with my code.

I am using a thread to listen for messages, while in the main code I am looping every second and sending data.

The purpose is to continually send data but also be able to not miss and quickly respond to a request.

def recv_msg_callback(topic, msg):
  BUSY = True
  print(topic +"="+ msg)
  
def listen(arg):
  while True:
    try:
      BUSY = False
      client.wait_msg()
    except NameError:
      pass

client.set_callback(recv_msg_callback)
client.subscribe('/lights')

_thread.start_new_thread(listen,(None,))

while True:
  if(not BUSY):
    print("Sending ON")
    client.publish("/slights", "ON")
    time.sleep(1)
    print("Sending OFF")
    client.publish("/slights", "OFF")
  time.sleep(1)

But the problem is, the main loop is not executing independently of the thread and only fires after a message is received.

The received data (lights=xxxxx) is being transmitted every 5 seconds (just for dev/testing) so what I am expecting is for the main look to send on and off 4 times for every receive but it is not.

Sending OFF
b'/lights=4639.61'
Sending ON
b'/lights=4644.02'
Sending OFF
b'/lights=4648.55'
Sending ON
b'/lights=4653.74'

What am I doing wrong ??