Connector

ROS 2

Replay ROS 2 bags or stream live topics

Category

Robotics

Kind

source

Capabilities

StreamsHistoryEntities

Runs on

Linux x64Linux ARM64macOS Apple siliconmacOS IntelWindows x64

Bring a robot's ROS 2 data into Phloem. Replay a bag from disk, or stream live topics over DDS or rosbridge. No ROS install is needed on this machine.

#Sources

Pick the Source first; only its settings show.

• Bag — replay a rosbag2 recording. Reads both mcap (the default since Iron) and sqlite3 (the default before it), split bags, metadata.yaml, and zstd compression in file and message mode. Speed 0 loads as fast as the disk allows. Loop replays over and over, each pass timed from now.
• DDS — join the robot's ROS 2 graph like another node. Set the robot's ROS_DOMAIN_ID (0 unless the robot sets one), on a network that reaches the robot. Topics are found with their types. Each subscription matches its publisher, so a latched topic like /tf_static still arrives. Leave the topic list blank to take every topic. Nothing runs on the robot.
• rosbridge — subscribe to live topics on a robot running rosbridge_server. Each topic's type is looked up before subscribing.

#What you get

• Joints — sensor_msgs/JointState becomes one channel per joint, named by the robot: /joint_states/position/left_hip_pitch, /joint_states/effort/left_hip_pitch, with units (rad, rad/s, N·m). A limit can watch one joint; a chart can pick the joints it wants.
• Diagnostics — diagnostic_msgs/DiagnosticArray (/diagnostics) gives channels per component: /diagnostics/left_wheel/level as a word (OK, WARN, ERROR, STALE, a state strip in Replay), /message, and one channel per key/value pair (/diagnostics/left_wheel/temperature, numeric when the value is a number). Names stay stable when the list reorders.
• Scene — point clouds, laser scans, TF transforms, 3D detections and camera images draw in the 3D view, in the frame the message names.
• Scene, the rest — paths and polygons, poses and odometry, occupancy grids, camera models, GPS fixes (on the map), and every marker type (arrows, cubes, spheres, cylinders, lines, points, text, meshes) draw in the 3D view, each marker under its own name.
• Everything else — flattened to topic/nested/field channels. A type with no definition arrives as raw bytes, with a warning naming the fix.

#Setup

1. Pick the source. Browse to a bag, or set the DDS domain or rosbridge URL.
2. The table lists each topic, its type, its message count, and the channels it will create.
3. Tick the topics to bring in.

#Message definitions

MCAP bags, and sqlite3 bags from Iron or later, carry their own type definitions. A Humble-era sqlite3 bag carries only type names. The standard interfaces (sensor_msgs, geometry_msgs, tf2_msgs, nav_msgs, vision_msgs, std_msgs, …) are built in, so those bags still decode.

For your own packages, point Message definitions at folders laid out as ROS packages (<dir>/<pkg>/msg/<Type>.msg). Your copy wins over the built-in one.

#Time

Choose header only when you trust the robot's clock. A simulator's clock counts from zero.

#Missing data

• Over DDS, samples this machine missed show as a gap on the topic's channels.
• Messages rosbridge_server dropped before sending cannot be seen.

#Supports

• rosbag2 recordings: mcap and sqlite3 storage, split bags, zstd file/message compression
• Bags from ROS 2 Humble and earlier (no embedded definitions) — the common ROS 2 interfaces are built in; add your own packages under Message definitions
• Live ROS 2 topics straight from the DDS graph (ROS_DOMAIN_ID, topics discovered with their types, each writer's reliability and durability matched) — no ROS install on this machine
• Live ROS 1 / ROS 2 topics over rosbridge_server (ws://host:9090) — no ROS install on this machine

#Connection fields

Every field the Add input form shows for this connector.

Updated November 6, 2026