Redirect messages from one MQTT server to another

mqtt_redirector.py

import sys
import time
import re
import paho.mqtt.client as mqtt


regex_address = re.compile(r'(?:(?P<username>.+):(?P<password>.+)@)?(?P<address>[\w.]+)(?::(?P<port>[0-9]+))?')

def on_message(client_src, userdata, message):
    client_dest, topic_root = userdata

    client_dest.publish(topic_root + message.topic, message.payload, message.qos, message.retain)

def connect_client(client, address):
    params = regex_address.match(address).groupdict()

    client.connect(params['address'], int(params['port']) if params['port'] else 1883)

    if params['username']:
        client.username_pw_set(params['username'], params['password'])

def redirect(broker_src_address, broker_dest_address, topic_root=''):
    client_dest = mqtt.Client('Redirector destination')
    client_src  = mqtt.Client('Redirector source', userdata=(client_dest, topic_root))

    connect_client(client_src,  broker_src_address)
    connect_client(client_dest, broker_dest_address)

    client_src.subscribe('#')
    client_src.on_message = on_message

    client_src.loop_start()
    client_dest.loop_forever()

if __name__ == '__main__':
    if len(sys.argv) < 3:
        print(f'usage: {sys.argv[0]} <src addr> <dest addr> [<topic root>]')
        sys.exit(0)

    if len(sys.argv) == 3:
        redirect(sys.argv[1], sys.argv[2])
    else:
        redirect(sys.argv[1], sys.argv[2], sys.argv[3])