RTPS Example

This example brings up an espp::RtpsParticipant on an ESP32-Ethernet-Kit and demonstrates every typed API the rtps component offers, interoperable with FastDDS / ROS 2 over the standard RTPS wire protocol.

It demonstrates:

  • Ethernet bring-up (DHCP server on 192.168.4.1/24, so a directly-attached PC gets an address) and starting a participant on the interface’s IPv4 address

  • a typed Publisher<StringMsg> / Subscriber<StringMsg> pair (reliable pub/sub) that pairs with the FastDDS host peer in pc/host_pubsub.cpp

  • a typed service server (/add_two_ints) and action server (/fibonacci) the device hosts — a ROS 2 client can drive them directly with ros2 service call / ros2 action send_goal (no manual CDR; reflectable AddReq/AddResp, FibGoal/FibSeq structs)

  • a typed service client + action client that call a peer’s /peer_add_two_ints / /peer_fib (run a ROS 2 / rclpy server for those names to see a full round-trip; otherwise the calls simply time out, still exercising the client API)

All of the RMI/AMI code is compiled out when RTPS_ENABLE_RPC is disabled.

How to use example

Configure

idf.py menuconfig

Under RTPS Example Configuration:

Option

Description

RTPS_EXAMPLE_ANNOUNCE_PERIOD_MS

Period of the outgoing publisher (default 1500 ms).

RTPS_EXAMPLE_SECOND_PARTICIPANT

Additively bring up a second, self-testing participant that calls the device’s own /add_two_ints + /fibonacci for a full on-device round-trip (default off; roughly doubles the RTPS engine RAM).

Under RTPS you can also toggle the limits profile, dynamic storage, DATA_FRAG fragmentation, and the RPC (services + actions) layer.

Build and Flash

idf.py -p PORT flash monitor

Replace PORT with the serial port. Connect the board’s Ethernet port to a PC (or a switch) so the participant has a network.

Talk to it

  • Pub/sub host peer (FastDDS): build and run pc/host_pubsub.cpp against the board’s topics.

  • ROS 2: with example_interfaces installed and on the same network/domain:

    ros2 service call /add_two_ints example_interfaces/srv/AddTwoInts "{a: 7, b: 35}"
ros2 action send_goal -f /fibonacci example_interfaces/action/Fibonacci "{order: 5}"

Expected Output

The monitor logs Ethernet link-up + the assigned IP, then tx/rx lines for the publisher/subscriber and service '/add_two_ints' + action '/fibonacci' ready. Each ROS 2 call logs the handled request/goal (e.g. service add_two_ints: 7 + 35 = 42, action fibonacci(5) done). With the second participant enabled, [self-test] lines report PASS/FAIL for the local round-trips.