ROS2 get publisher node name from subscriber

edit

Following the trace of the command line ros2 topic infoleads us here: https://github.com/ros2/ros2cli/blob/... From there we can see that the rclcpp Graph API contains the methods. I quickly tried something out:

launch this in a terminal: ros2 run demo_nodes_cpp talker

And run the following code:

#include <chrono>
#include <functional>
#include <memory>
#include <string>

#include "rclcpp/rclcpp.hpp"


class MinimalPublisher : public rclcpp::Node
{
  public:
    MinimalPublisher()
    : Node("minimal_publisher"), count_(0)
    {
      timer_ = this->create_wall_timer(
      500ms, std::bind(&MinimalPublisher::timer_callback, this));
    }

  private:
    void timer_callback()
    {
      auto result = this->get_publishers_info_by_topic("/chatter");
      for(const auto& node : result)
      {
        std::cout << node.node_name() << " topic type: " << node.topic_type() << " qos history: " << node.qos_profile().get_rmw_qos_profile().history <<  std::endl;
      }
    }
    rclcpp::TimerBase::SharedPtr timer_;
};

int main(int argc, char * argv[])
{
  rclcpp::init(argc, argv);
  rclcpp::spin(std::make_shared<MinimalPublisher>());
  rclcpp::shutdown();
  return 0;
}

This outputs:

ros2 run graph_node graph_node 
talker topic type: std_msgs/msg/String qos history: 3
talker topic type: std_msgs/msg/String qos history: 3
talker topic type: std_msgs/msg/String qos history: 3