A very, **very** basic ROS MQTT Bridge using `rosbridge_library` and `paho.mqtt`

rosbridge_mqtt.py

import json

import paho.mqtt.client as mqtt
import rospy
from loguru import logger
from paho.mqtt.subscribe import simple
from rosbridge_library.rosbridge_protocol import RosbridgeProtocol

# The following parameters are passed on to RosbridgeProtocol
# defragmentation.py:
fragment_timeout = 600  # seconds
# protocol.py:
delay_between_messages = 0  # seconds
max_message_size = None  # bytes
unregister_timeout = 10.0  # seconds

mqtt_publisher = mqtt.Client("rosbridge_mqtt")
mqtt_publisher.connect("localhost")


def process_message(message=None):
    obj = json.loads(message)
    topic = obj["topic"]
    msg = obj["msg"]
    payload = json.dumps(msg)
    try:
        mqtt_publisher.publish(topic, payload)
    except Exception as e:
        logger.error(f"Error publishing message to MQTT: {str(e)}")


if __name__ == "__main__":
    rospy.init_node("mqtt_bridge")

    parameters = {
        "fragment_timeout": fragment_timeout,
        "delay_between_messages": delay_between_messages,
        "max_message_size": max_message_size,
        "unregister_timeout": unregister_timeout
    }

    rb_prot = RosbridgeProtocol(0, parameters=parameters)
    rb_prot.outgoing = process_message

    while not rospy.is_shutdown():
        msg = simple("rosbridge")
        logger.info(f"Message {msg.payload.decode()}")
        rb_prot.incoming(msg.payload.decode())