jcmonteiro
commented
2 years ago Service Request
Looks like there is some incorrect behavior either
- in the serialization happening on the agent, or
- in extracting the UDP data from the UDP packet.
Running the agent in debug mode shows that the request of the AddTwoInts, two int64_t integers of 8 bytes each, is transmitted in a UDP packet containing 68 bytes (8 for the header + 60 for the data), thus 60 bytes of data instead of 16. The values of variables int64_t a and int64_t b are present in the last 16 bytes of the UDP packet. I don't know if this is intended behavior, but it is not matching the deserialization happening in the MCU side.
The MCU receives the UDP packet when the service is called and writes the last 32 bytes in a buffer. This can be validated by adding a breakpoint at rmw_microxrcedds/rmw_microxrcedds_c/src/rmw_request.c#L124 and validating the contents of static_buffer->buffer and static_buffer->length.
The buffer is then sent for deserialization, but it deserialized incorrectly since it expects the data to be at the beginning of the buffer and, in this case, the data is present after a 16 bytes offset.
Service Response
I still need to dig a little deeper, but there might be a similar issue (namely inconsistent serialization/deserialization) happening on the response. I say this because running the agent in debug mode clearly shows that the agent receives a UDP packet containing ~the~ a response. The data, int64_t sum, is present in the last 8 bytes of a 32 bytes UDP packet (8 bytes header + 16 bytes unknown + 8 bytes data).
Issue template
Steps to reproduce the issue
ros2 run micro_ros_setup configure_firmware.sh add_two_ints_service --transport udp --ip <our agent ip> --port 8888ros2 service call /addtwoints example_interfaces/srv/AddTwoInts "{a: 5, b: 10}"Expected behavior
Should get a response (sum=15)
Actual behavior
waiting for service to become available... requester: making request: example_interfaces.srv.AddTwoInts_Request(a=5, b=10)Additional information
We basically have the same issue as this but with FreeRTOS on our STM32 board. We using a router from Teltonika- RUT240 (which a decent router), and the computer running the agent and making service calls is connected though Ethernet.
Quick note: I had to include
#include <rclc/executor.h>in the example code, and change "printk"s to printf to get it to compile.Not very well-versed with uROS or DDS stuff, but we tried the following:
export RMW_IMPLEMENTATION=rmw_fastrtps_cppbefore starting the agent, as suggested in this thread.Logs from the agent: