#include <ros.h>
#include <std_msgs/String.h>
#include <std_srvs/Empty.h>

ros::NodeHandle nh;

bool messageCb(std_srvs::Empty::Request &req, std_srvs::Empty::Response &res) {
  digitalWrite(LED_BUILTIN, HIGH-digitalRead(LED_BUILTIN));   // blink the led
  
  nh.loginfo("LED is ON");
  
  return true;
}

ros::ServiceServer<std_srvs::Empty::Request, std_srvs::Empty::Response> blinkServer("/led/blink", &messageCb);

void setup()
{
  pinMode(LED_BUILTIN, OUTPUT);
  nh.initNode();
  nh.advertiseService(blinkServer);
}

void loop()
{
  digitalWrite(LED_BUILTIN, HIGH);  // turn the LED on (HIGH is the voltage level)
  delay(10);                      // wait for a second
  digitalWrite(LED_BUILTIN, LOW);   // turn the LED off by making the voltage LOW
  delay(10);                      // wait for a second  
  nh.spinOnce();
}