ros2 network_error ai_generated true

RMW_IMPLEMENTATION mismatch: publisher and subscriber on different middleware implementations cannot communicate

ID: ros2/rmw-implementation-mismatch-discovery-failure

Also available as: JSON · Markdown · 中文
85%Fix Rate
88%Confidence
1Evidence
2023-06-15First Seen

Version Compatibility

VersionStatusIntroducedDeprecatedNotes
Humble active — — —
Iron active — — —
Rolling active — — —

Root Cause

ROS2 nodes must use the same RMW implementation (e.g., rmw_fastrtps_cpp vs rmw_cyclonedds_cpp) to discover each other and exchange messages, due to incompatible DDS protocol variants or transport layers.

generic

中文

ROS2节点必须使用相同的RMW实现（如rmw_fastrtps_cpp与rmw_cyclonedds_cpp）才能相互发现并交换消息，因为DDS协议变体或传输层不兼容。

Official Documentation

https://docs.ros.org/en/rolling/How-To-Guides/Working-with-multiple-RMW-implementations.html

Workarounds

  1. 90% success Set the same RMW_IMPLEMENTATION environment variable for all nodes. For example, in a launch file or shell: export RMW_IMPLEMENTATION=rmw_fastrtps_cpp. Then restart all nodes. 
    Set the same RMW_IMPLEMENTATION environment variable for all nodes. For example, in a launch file or shell: export RMW_IMPLEMENTATION=rmw_fastrtps_cpp. Then restart all nodes.
  2. 85% success If using Cyclone DDS, install the rmw_cyclonedds_cpp package and set RMW_IMPLEMENTATION=rmw_cyclonedds_cpp on all machines. For Fast DDS, use rmw_fastrtps_cpp. Run 'ros2 doctor' to verify current RMW. 
    If using Cyclone DDS, install the rmw_cyclonedds_cpp package and set RMW_IMPLEMENTATION=rmw_cyclonedds_cpp on all machines. For Fast DDS, use rmw_fastrtps_cpp. Run 'ros2 doctor' to verify current RMW.
  3. 80% success To check current RMW: echo $RMW_IMPLEMENTATION. If unset, default is rmw_fastrtps_cpp. Use 'ros2 run demo_nodes_cpp talker' and 'listener' on the same RMW to test discovery. 
    To check current RMW: echo $RMW_IMPLEMENTATION. If unset, default is rmw_fastrtps_cpp. Use 'ros2 run demo_nodes_cpp talker' and 'listener' on the same RMW to test discovery.

中文步骤

  1. Set the same RMW_IMPLEMENTATION environment variable for all nodes. For example, in a launch file or shell: export RMW_IMPLEMENTATION=rmw_fastrtps_cpp. Then restart all nodes.
  2. If using Cyclone DDS, install the rmw_cyclonedds_cpp package and set RMW_IMPLEMENTATION=rmw_cyclonedds_cpp on all machines. For Fast DDS, use rmw_fastrtps_cpp. Run 'ros2 doctor' to verify current RMW.
  3. To check current RMW: echo $RMW_IMPLEMENTATION. If unset, default is rmw_fastrtps_cpp. Use 'ros2 run demo_nodes_cpp talker' and 'listener' on the same RMW to test discovery.

Dead Ends

Common approaches that don't work:

  1. 95% fail

    Changing ROS_DOMAIN_ID only helps with network segmentation, not RMW incompatibility. Nodes on different RMWs will still not discover each other even on the same domain.

  2. 90% fail

    RMW mismatch is a protocol-level issue, not a network routing problem. Tuning discovery interfaces doesn't change the underlying DDS implementation incompatibility.

  3. 75% fail

    This only sets the default RMW at build time. If environment variable RMW_IMPLEMENTATION is set differently at runtime, the build-time setting is overridden.