Merge pull request #2 from benjaminwp18/basic-node

Basic node

.gitignore

@@ -1,5 +1,7 @@
+install/
 devel/
 logs/
+log/
 build/
 bin/
 lib/

README.md

@@ -3,3 +3,29 @@
 [![Continuous Integration](https://github.com/benjaminwp18/mqtt_ros_bridge/actions/workflows/industrial_ci_action.yml/badge.svg)](https://github.com/benjaminwp18/mqtt_ros_bridge/actions/workflows/industrial_ci_action.yml)
 
 A ROS2 package for bridging between MQTT and ROS networks
+
+## Installation
+### Operating System
+ROS2 is pretty tightly coupled to Ubuntu versions. `mqtt_ros_bridge` supports ROS2 Iron Irwini and Humble Hawksbill. Pick a [version](https://docs.ros.org/en/rolling/Releases.html) that works with your OS.
+
+### MQTT
+Install an MQTT broker like [Mosquitto](https://mosquitto.org/).
+
+```bash
+sudo apt-get update
+sudo apt-get install mosquitto mosquitto-clients -y
+```
+
+Your broker should now be running:
+```bash
+you@ubuntu:~ $ service mosquitto status
+● mosquitto.service - Mosquitto MQTT v3.1/v3.1.1 Broker
+   Loaded: loaded (/lib/systemd/system/mosquitto.service; enabled; vendor preset
+   Active: active (running) since Sat 2021-01-30 16:46:20 GMT; 1min 23s ago
+     Docs: man:mosquitto.conf(5)
+           man:mosquitto(8)
+ Main PID: 5390 (mosquitto)
+    Tasks: 1 (limit: 2063)
+   CGroup: /system.slice/mosquitto.service
+           └─5390 /usr/sbin/mosquitto -c /etc/mosquitto/mosquitto.conf
+```

launch/bridge_launch.py

@@ -0,0 +1,24 @@
+from launch.launch_description import LaunchDescription
+from launch_ros.actions import Node
+
+
+def generate_launch_description() -> LaunchDescription:
+    """
+    Generate LaunchDescription for MQTT ROS bridge.
+
+    Returns
+    -------
+    LaunchDescription
+        Launches bridge_node.
+
+    """
+    run_bridge_node = Node(
+        package='mqtt_ros_bridge',
+        executable='bridge_node',
+        emulate_tty=True,
+        output='screen'
+    )
+
+    return LaunchDescription([
+        run_bridge_node
+    ])

mqtt_ros_bridge/bridge_node.py

@@ -0,0 +1,107 @@
+from typing import Any
+from dataclasses import dataclass
+
+import rclpy
+from rclpy.node import Node
+from rclpy.publisher import Publisher
+from rclpy.subscription import Subscription
+
+from std_msgs.msg import String
+
+import paho.mqtt.client as MQTT
+
+
+@dataclass
+class TopicInfo():
+    """Metadata about a single topic."""
+
+    name: str
+    publish_on_ros: bool
+
+
+TOPICS: list[TopicInfo] = [
+    TopicInfo('pub_topic', True),
+    TopicInfo('sub_topic', False)
+]
+
+
+class BridgeNode(Node):
+    """Node to bridge MQTT and ROS."""
+
+    def __init__(self) -> None:
+        super().__init__('mqtt_bridge_node')
+
+        print('Creating MQTT ROS bridge node')
+
+        self.mqtt_client = MQTT.Client()
+        self.mqtt_client.enable_logger()
+        self.mqtt_client.connect('localhost', port=1883, keepalive=60)
+        self.mqtt_client.loop_start()
+
+        self.ros_publishers: dict[str, Publisher] = {}
+        self.ros_subscriptions: list[Subscription] = []
+
+        for topic_info in TOPICS:
+            if topic_info.publish_on_ros:
+                publisher = self.create_publisher(String, topic_info.name, 10)
+                self.ros_publishers[topic_info.name] = publisher
+                self.mqtt_client.subscribe(topic_info.name)
+            else:
+                subscription = self.create_subscription(
+                    String, topic_info.name, self.make_ros_receiver(topic_info.name), 10)
+                self.ros_subscriptions.append(subscription)
+
+        self.mqtt_client.on_message = self.mqtt_msg_received
+
+    def make_ros_receiver(self, topic: str):
+        """
+        Create a callback function which re-publishes messages on the same topic in MQTT.
+
+        Parameters
+        ----------
+        topic : str
+            the topic that the callback will publish on
+
+        """
+        def callback(msg: String):
+            self.get_logger().info(f"ROS RECEIVED: Topic: '{topic}' Payload: '{msg}'")
+            self.mqtt_client.publish(topic, msg.data)
+
+        return callback
+
+    def mqtt_msg_received(self, _client: MQTT.Client, _userdata: Any, mqtt_msg: MQTT.MQTTMessage):
+        """
+        Re-publish messages from MQTT on the same topic in ROS.
+
+        Parameters
+        ----------
+        _client : MQTT.Client
+            unused; the MQTT client which received this message
+        _userdata : Any
+            unused; the private user data as set for the client
+        mqtt_msg : MQTT.MQTTMessage
+            the message received over MQTT
+
+        """
+        self.get_logger().info(
+            f"MQTT RECEIVED: Topic: '{mqtt_msg.topic}' Payload: '{mqtt_msg.payload!r}'")
+
+        ros_msg = String()
+        ros_msg.data = mqtt_msg.payload.decode('utf-8')
+        self.ros_publishers[mqtt_msg.topic].publish(ros_msg)
+
+
+def main(args=None):
+    """Run bridge node; used in ROS executable."""
+    rclpy.init(args=args)
+
+    bridge_node = BridgeNode()
+
+    rclpy.spin(bridge_node)
+
+    bridge_node.destroy_node()
+    rclpy.shutdown()
+
+
+if __name__ == '__main__':
+    main()

package.xml

@@ -9,8 +9,10 @@
   <license>Apache License 2.0</license>
 
   <depend>rclpy</depend>
+  <depend>python3-paho-mqtt</depend>
 
   <exec_depend>ros2launch</exec_depend>
+  <exec_depend>std_msgs</exec_depend>
 
   <test_depend>ament_flake8</test_depend>
   <test_depend>ament_pep257</test_depend>

setup.py

@@ -26,6 +26,7 @@
     tests_require=['pytest'],
     entry_points={
         'console_scripts': [
+            'bridge_node = mqtt_ros_bridge.bridge_node:main'
         ],
     },
 )