ROS Toolbox Fast CDR exception deserializing message of type rmw_dds_common...

Problem: When a python publisher is set up and a MatLab subscriber is on the same domain, creating the subscriber or running ros2 topic list in the Matlab terminal will return this error;

[rcutils|error_handling.c:108] rcutils_set_error_state()
This error state is being overwritten:

  ''Bad alloc' exception deserializing message of type rmw_dds_common::msg::dds_::ParticipantEntitiesInfo_., at ./src/type_support_common.cpp:123'

with this new error message:

  'Fast CDR exception deserializing message of type rmw_dds_common::msg::dds_::ParticipantEntitiesInfo_., at ./src/type_support_common.cpp:118'

rcutils_reset_error() should be called after error handling to avoid this.

This then repeats about 5 times, which then leads to substantial lag, followed by either Matlab crashing (100% RAM and CPU usage) or the system running smoothly without crashing, seemingly unaware of the issue. This also repeats when the subscriber is closed.

The code I have is very simple.

Python:

# simple_pub_float64multiarray.py
# Publishes an example float64multiarray on the "tester" topic

import rclpy
import math
from rclpy.node import Node

from std_msgs.msg import Float64MultiArray

class MinimalPublisher(Node):

    def __init__(self):
        super().__init__('minimal_publisher')
        self.publisher_ = self.create_publisher(Float64MultiArray, 'tester', 10)
        timer_period = 0.2  # seconds
        self.timer = self.create_timer(timer_period, self.timer_callback)
        self.i = 1.0

    def timer_callback(self):
        msg = Float64MultiArray()
        msg.data = [42.0, 10.0, 9.0]
        self.publisher_.publish(msg)
        self.get_logger().info('%s' % msg)
        self.i += 1


def main(args=None):
    rclpy.init(args=args)

    minimal_publisher = MinimalPublisher()

    rclpy.spin(minimal_publisher)

    minimal_publisher.destroy_node()
    rclpy.shutdown()


if __name__ == '__main__':
    main()

Matlab:

    matlabSubNodeName = "matlab_receiver";
matlabSubNode = ros2node(matlabSubNodeName);

subscriber = ros2subscriber(matlabSubNode, "/tester", @testSub, "Reliability", "besteffort");

function testSub(msg)
    disp(msg.data)
end

Additional Information: I am on Matlab 2025a, using Python 3.10, and have tried both cyclone_dds and fastrtps_dds. Both my Ubuntu and Matlab are using ROS2 Humble. When running these very simple scripts, the chances of crashing are low; however, I am having to connect a large amount of subscribers due to how my code is structured, which increases the chance of a crash occuring.

I have also received the following errors when using cyclone_dds instead of fastrtps_dds;

Error; This error state is being overwritten:

  'invalid data size, at ./src/serdata.cpp:384'

with this new error message:

  'string data is not null-terminated, at ./src/serdata.cpp:384'

I have also gotten this error in the terminal I am using to run Matlab;

  [WARN] [1751049296.108842927] [rmw_cyclonedds_cpp]: Failed to parse type hash for topic 'ros_discovery_info' with type 'rmw_dds_common::msg::dds_::ParticipantEntitiesInfo_' from USER_DATA '(null)'.

Some assistance would be greatly appreciated.

Answer 1

[George Wu]

Hi,

This also happened to me when I migrated from R2024a to R2025a. In my matlab log, there was a warning saying ROS_LOCALHOST_ONLY is deprecated but still honored if it is enabled. Use ROS_AUTOMATIC_DISCOVERY_RANGE and ROS_STATIC_PEERS instead.

I've then checked the environment setting by `getenv('ROS_LOCALHOST_ONLY')`, where ROS_LOCALHOST_ONLY was set to 0, where no values should be set, as the exception handler in ROS2 apparently causes lag.

I've fixed it by adding a line `setenv('ROS_LOCALHOST_ONLY', '');`

Regards,

George