Background

A charge point must send a StatusNotification CALL to the CSMS whenever a connector's operational state changes. This is how the CSMS tracks connector availability in real time — without it, the CSMS never knows whether connectors are available, charging, faulted, etc.

The Python reference handles this in ocpp/v16/call.py:

@dataclass
class StatusNotification:
    connector_id: int
    error_code: enums.ChargePointErrorCode
    status: enums.ChargePointStatus
    timestamp: Optional[str] = None
    info: Optional[str] = None
    vendor_id: Optional[str] = None
    vendor_error_code: Optional[str] = None

The current Rust ChargePoint never sends StatusNotification, even as connector state transitions happen inside TransactionManager. This means a connected CSMS has no visibility into connector state.

What needs to change

1. ChargePoint::send_status_notification(connector_id, status, error_code) — sends StatusNotificationRequest via call(). Timestamp set to Utc::now().
2. Automatic notifications on state transitions — start_transaction() and stop_transaction() should send StatusNotification to reflect each state change:
   • Before auth: Available → Preparing
   • After StartTransactionResponse accepted: Preparing → Charging
   • After StopTransactionRequest sent: Charging → Finishing → Available
3. On connect / after boot: send StatusNotification(connector_id=0, status=Available, error_code=NoError) for each configured connector.
4. CSMS handler on the server side: default on_status_notification handler in OcppServer that logs the status change and emits a TransportEvent::StatusNotification { cp_id, connector_id, status }.

Acceptance criteria

• ChargePoint::send_status_notification(connector_id: u32, status: ChargePointStatus, error_code: ChargePointErrorCode) -> OcppResult<()> implemented
• Called automatically during transaction lifecycle:
  • start_transaction(): sends Preparing before authorize, Charging after accepted start
  • stop_transaction(): sends Finishing, then Available after stop confirmed
• After boot accepted: sends StatusNotification(connector_id=0, status=Available, error_code=NoError) for each connector
• ChargePointErrorCode::NoError is the default for normal state transitions
• Tests:
  • status_notification_sent_on_start_transaction — verify Preparing → Charging frames
  • status_notification_sent_on_stop_transaction — verify Finishing → Available frames
  • status_notification_sent_after_boot_accepted — connector 0 Available after boot
  • send_status_notification_custom_error_code — sends with specified error code
• cargo fmt --check, cargo clippy --all-targets -- -D warnings, cargo test --workspace all pass

Python reference

• ocpp/v16/call.py — StatusNotification dataclass
• ocpp/v16/call_result.py — StatusNotification response (empty {})
• ocpp/v16/enums.py — ChargePointStatus, ChargePointErrorCode
• OCPP 1.6J spec §3.14 — Status Notification use case

Dependencies

• Depends on Issue feat(transactions): wire StartTransaction/StopTransaction OCPP messages into ChargePoint (M3) #21 (StartTransaction/StopTransaction OCPP messages) being complete — start_transaction() and stop_transaction() must send OCPP messages before StatusNotification can be woven in
• Depends on Issue ChargePoint boot sequence: send BootNotification on connect, retry on Rejected/Pending, start heartbeat loop (M2) #20 (BootNotification boot sequence, PR feat(cp): BootNotification boot sequence + CSMS-supplied heartbeat interval (Issue #20) #26) — send_status_notification after boot requires the boot sequence to complete
• Part of M4 CP simulator milestone