Flutter + ROS 2 Commands: Low-Latency UI With Explicit Acknowledgements

#flutter #ros2 #robotics #safety

Flutter + ROS 2 Commands: Low-Latency UI With Explicit Acknowledgements

Operator commands should not be treated like replaceable telemetry. A responsive button is only one part of the system; the client needs to distinguish submitted, accepted, executing, completed, and rejected states.

Model the command lifecycle

Assign a unique command ID and expose explicit lifecycle states. Do not show success merely because a request was written to a socket.

Keep commands separate from telemetry

Do not queue critical commands behind camera metadata or diagnostics. Use a dedicated path with authentication, authorization, timeouts, and rate limits.

Prevent duplicate actions

Disable or debounce controls while pending where appropriate, but make the server idempotent using command IDs.

Show uncertainty honestly

If the connection drops after submission, show outcome unknown until reconciled. Do not blindly resend a non-idempotent command.

Test delay and disconnection

Inject slow acknowledgements, duplicate responses, gateway restarts, and reordered events.

Example implementation

This Dart snippet illustrates one part of the design. Adapt types, transport behavior, timestamp semantics, and platform APIs to your actual system before production use.

enum CommandPhase {
  idle, submitting, accepted, executing, completed, rejected, outcomeUnknown
}

class CommandStatus {
  const CommandStatus(this.id, this.phase);
  final String id;
  final CommandPhase phase;
}

Performance checklist

Measure p95/p99 behavior on target hardware, not only a desktop simulator.
Bound queues and buffers; define what may be coalesced or dropped.
Keep heavy parsing, image processing, and inference away from the Flutter UI thread.
Track source timestamps, sequence numbers, stale-data rate, and dropped updates.
Test network degradation, reconnects, sustained operation, and resource pressure.
Keep control commands and critical alerts separate from replaceable telemetry.