mqtt_app_bridge.py

import json
import paho.mqtt.client as paho
import signal

broker="192.168.0.32"
port=1883

received_data = []

class GracefulKiller:
  kill_now = False
  def __init__(self):
    signal.signal(signal.SIGINT, self.exit_gracefully)
    signal.signal(signal.SIGTERM, self.exit_gracefully)

  def exit_gracefully(self, *args):
    self.kill_now = True

def on_message(client, userdata, message):
    data = json.loads(message.payload)
    received_data.append(data)    

if __name__ == '__main__':
    killer = GracefulKiller()    

    mqClient = paho.Client("Prototracer_bridge")  # create client object
    mqClient.connect(broker, port)  # establish connection
    mqClient.on_message=on_message
    mqClient.subscribe("dev/prototracer")
    mqClient.loop_start()

    while not killer.kill_now:
        with open('./data_pipe_fifo', 'w') as f:
            if len(received_data) > 0:
                data = received_data.pop(0)
                out = f"{data['cmd']}:" + ":".join(data['dat'])
                print(f"Writing: {out}")
                f.write(out)
                f.flush()
    f.close()