led_panel.py

#!/usr/bin/env python3
import rclpy
from rclpy.node import Node

from my_interfaces.msg import LedStateArray
from my_interfaces.srv import SetLed


class LedPanelNode(Node): 

    def __init__(self):
        super().__init__("led_panel")
        self.led_states_ = [0, 0, 0]
        self.led_states_publisher_ = self.create_publisher(
            LedStateArray, "led_states", 10)
        self.led_states_timer = self.create_timer(4, self.publish_led_states)
        self.set_led_service_ = self.create_service(
            SetLed, "set_led", self.callback_set_led)
        self.get_logger().info("Led panel node has been started.")
    
    def publish_led_states(self):
        msg = LedStateArray()
        msg.led_states = self.led_states_
        self.led_states_publisher_.publish(msg)
    
    def callback_set_led(self, request, response):
        led_num = request.led_number
        state = request.state

        # The led exist
        if led_num > len(self.led_states_)or led_num <= 0:
            response.success = False
            return response

        # The state is False(0) or True(1)s
        if state not in [0, 1]:
            response.succes = False
            return response

        self.led_states_[led_num - 1] = state 
        response.success = True
        self.publish_led_states()
        return response



def main(args=None):
    rclpy.init(args=args)
    node = LedPanelNode()
    rclpy.spin(node)
    rclpy.shutdown()


if __name__ == "__main__":
    main()