mros2 node name cannot be observed from ROS 2 host

[takasehideki]

We cannot observe the name of mros2 nodes from ROS 2 host, e.g., by ros2 node list.

We think this is due to the functionality limitation of embeddedRTPS, which is employed as the RTPS layer for mROS 2. While topic names in ROS2 are realized using standard DDS functions, node names seem to be implemented as a unique feature in ROS2. Officially supported DDS for ROS 2 (e.g., FastDDS) seems to work with RCL and RMW to achieve node names. We think it is unrealistic to allow embeddedRTPS to handle node names as a feature, because it is just an RTPS stack used as the standalone software for the embedded devices. Therefore, we should realize this feature in the mROS 2 hierarchy to be able to handle node names because mROS 2 corresponds to RCL and RMW layers.

[takasehideki]

added as the limitation on README 6532fc1

[takasehideki]

The followings is the code space on ROS 2 implementation that may help us (I hope,,,;(

• ros2/ros2cli:
  • implementation of ros2 node: https://github.com/ros2/ros2cli/blob/rolling/ros2node/ros2node/api/__init__.py
  • its internal: https://github.com/ros2/ros2cli/blob/rolling/ros2node/ros2node/verb/list.py
  • function to get node names (and namespaces): https://github.com/ros2/ros2cli/blob/c43e064b25c94dccce3e8922081faf76b7c62b7c/ros2cli/ros2cli/daemon/__init__.py#L84
• ros2/rclpy:
  • get_node_names: https://github.com/ros2/rclpy/blob/540b809b1b4d6fc064cfd392834123f713593be4/rclpy/rclpy/node.py#L2004
  • get_names_impl: https://github.com/ros2/rclpy/blob/540b809b1b4d6fc064cfd392834123f713593be4/rclpy/src/rclpy/node.cpp#L112
• ros2/rcl:
  • create_node: https://github.com/ros2/rcl/blob/799151f96f8c7568a915b43bdc4e97013865a2ea/rcl/src/rcl/node.c
  • relation to rmw_node_t: https://github.com/search?q=repo%3Aros2%2Frmw%20rmw_node_t&type=code
• ros2/rmw:
  • struct for node including name https://github.com/ros2/rmw/blob/83445be486deae8c78d275e092eafb4bf380bd49/rmw/include/rmw/types.h#L47-L63