# Heidenhain LSV2 driver (read-only)

`DriverType = "Heidenhain"` (`DriverTypeNames.Heidenhain`) · projects `Driver.Heidenhain` (+ `.Contracts`) ·
Gitea **#803**.

A native, **read-only** Heidenhain LSV2 client over TCP (default port **19000**) for iTNC/TNC controls. No
Java/Python runtime and no vendor SDK (RemoTools/DNC) — a managed `System.Net.Sockets` client. It is a port of the
ignitionoee v0.20.3 Java driver (commit `d1dda0a5`, `modules/drivers/gateway/.../driver/heidenhain`, wire reference
`docs/reference/heidenhain-lsv2.md`), whose protocol layouts are in turn derived from pyLSV2 commit `97a3d691`.
**The Java validation evidence (four real iTNC 530 controls, 2026-11-03) is reference evidence, not proof of this
port** — see [Hardware-gated](#hardware-gated--not-yet-proven).

## Read-only boundary

Three independent layers, each sufficient on its own for its concern:

1. **No write capability.** `HeidenhainDriver` does not implement `IWritable`; `DriverInstanceActor` refuses every
   OPC write before it reaches the driver (`HeidenhainDriverEndToEndTests`).
2. **No writable nodes.** A `ReadWrite` access level is refused at **authoring** — `RawTreeService`
   create/update/import (so the tag modal, manual entry, CSV import and browse commit), where the modal and the
   manual-entry grid also fix the access level at Read — and again by the deploy gate `HeidenhainTagWritable`, so no
   node is ever advertised writable. A `"writable": true` TagConfig key is rejected by the tag reader and dropped by
   the typed editor. The same paths tie `Tag.DataType` to what the driver publishes (the catalog type for a fixed
   address — `Float64` ⇒ `Double` — or the binding's declared type): the modals default it from the address, the
   save path refuses a mismatch, and the deploy gate `HeidenhainTagDataTypeMismatch` catches anything older
   (one rule, `HeidenhainTagRules`).
3. **Payload-aware outbound allowlist** (`Lsv2ReadOnlyPolicy`). `Lsv2Codec.Frame` — the only frame builder — checks
   command **and** payload immediately before any byte is written. There is no raw-command API (`Lsv2Client`'s
   public surface is pinned by a reflection test) and no configuration knob that widens it.

| Request | Permitted payload | Reply |
|---|---|---|
| `A_LG` | role ∈ {`INSPECT`, `DNC`, `DATA`} NUL, optional NUL-free Latin-1 password NUL | `T_OK` (empty) |
| `R_VR` | empty | `S_VR` |
| `R_PR` | empty | `S_PR` |
| `R_RI` | exactly a uint16be selector ∈ {22–28, 30–34, 51} | `S_RI` |
| `R_MB` | uint32be address + uint8 count, 1 ≤ count ≤ 247, no 32-bit wrap | `S_MB` |
| `R_DP` | four zero bytes + NUL-free path + NUL (≤ 247 bytes total) | `S_DP` |

Everything else is refused before transmission — every `C_*` (file/PLC/parameter writes, buffer negotiation),
`A_LO`, file reads (`R_FL`, `R_DI`, …), key/scope operations, `PLCDEBUG`/`MONITOR`/`FILE` roles, response
mnemonics sent as requests. `Lsv2ReadOnlyPolicyTests.A_refused_request_never_reaches_the_socket` proves zero bytes
leave the process for a refused request, even through the internal exchange primitive. Socket close ends a
session (no logout command). **Do not broaden the allowlist to work around a controller refusal.**

## Transport

`uint32be payloadLength | ASCII command[4] | payload` — legacy buffer mode, 255-byte frame maximum, no `C_CC`
negotiation. One transaction at a time per control (a `SemaphoreSlim` in `Lsv2Client`, and a single acquisition
loop per device). Each transaction has **one monotonic deadline** (`TimeoutMs`) covering write + header + body, so a
trickling peer cannot extend it. EOF, deadline, an oversized (> 247) or unexpected reply, a malformed `T_ER`, or a
`T_OK` with a body **closes the client** — a later request can never consume leftover bytes. A complete
`T_ER`/`T_BD` refusal keeps the stream synchronised. `Close()` never waits for the transaction gate, so it always
interrupts a blocked read.

## Configuration

Driver config (`HeidenhainDriverOptions`, AdminUI **HeidenhainDriverForm**) — every field is int/bool/string (no
enums, so the numeric-enum form/factory trap cannot occur):

| Key | Default | Range / meaning |
|---|---|---|
| `TimeoutMs` | 5000 | 100–60000; connect + per-transaction deadline |
| `Access.TelemetryEnabled` | true | Off = no `R_RI` requests at all |
| `Access.DncLoginEnabled` | true | Optional DNC login; a refusal never blocks reads permitted under INSPECT |
| `Access.DataEnabled` | false | Opt-in DATA login, attempted only when a `DATA:` binding exists (iTNC only) |
| `Access.InspectPassword` / `DncPassword` / `DataPassword` | — | **References only** (below) |
| `Polling.StatusMs` / `CustomMs` / `SlowMs` | 1000 / 1000 / 10000 | each 100–3600000 |
| `Polling.MaxAlarms` | 64 | 1–256 |
| `Polling.TimersEnabled` | **false** | Experimental selectors 30–34 |
| `Reconnect.InitialDelayMs` / `MaxDelayMs` | 1000 / 30000 | doubling backoff, bounded |
| `ProbeTimeoutSeconds` | 10 | Test Connect, 1–60 |

Device config (one `/raw` Device per control, AdminUI **HeidenhainDeviceForm**): `Host` (required, no default),
`Port` (19000), optional per-device `InspectPassword`/`DncPassword`/`DataPassword` overrides. A device is validated
only once it carries tags, so an unconfigured default `Device1` does not fault the driver.

**Credentials — namespaced references only.** A password field is one of:

| Form | Resolved from |
|---|---|
| blank | no password |
| `secret:heidenhain/<name>` (e.g. `secret:heidenhain/line3/inspect`; `[A-Za-z0-9._-]` segments, no `..`) | the node's encrypted secret store (`ISecretResolver`), same slash-scoped naming as `galaxy/<inst>/apikey` |
| `env:OTOPCUA_HEIDENHAIN_<NAME>` (exact upper-case prefix, `NAME` = `[A-Z0-9_]+`) | the process environment |

**Why namespaced:** the reference is resolved on the node (for Test Connect: on the admin node) and sent in
**cleartext** in `A_LG` to whatever Host the author configured. An unscoped reference would let anyone who can edit
a driver exfiltrate `env:ConnectionStrings__ConfigDb`, `env:ServerHistorian__ApiKey` or any other secret by pointing
Host at their own machine. Anything outside the namespace is refused by **every** layer: the parser
(`HeidenhainOptionsParser`, so the factory and the probe), the resolver **again at resolve time**
(`HeidenhainCredentials`, fail-closed independently of earlier validation), the AdminUI **save path**
(`RawTreeService` create/update driver + device refuse the config server-side via `DriverConfigSaveGate`, and the
driver/device modals disable Save while it is invalid — so a literal never reaches the config database), and the
deploy gate `HeidenhainCredentialPersisted`. Messages never echo the value.

Resolved **at each login**, never held in options or session state. Fail-closed: an absent secret or unset
variable fails the login rather than sending the reference text. An unusable **INSPECT** credential fails the
connect (INSPECT is required). An unusable **optional** DNC/DATA credential — unresolvable, or a password the LSV2
login payload cannot carry (NUL, non-Latin-1, &gt; 247 bytes) — never fails the session: the login is not sent, the
reads that need that role read `BadConfigurationError` (capability `ConfigurationError`), and INSPECT telemetry
continues. Plain LSV2 is unencrypted — reach the control over an externally managed secure network; there is no
SSH subsystem.

## Addresses (TagConfig)

`{"address": "<address>", "dataType": "<DriverDataType name>", "isArray": true|false}` — parsed by
`HeidenhainTagDefinitionFactory`, the single authority shared by the driver, the deploy inspector
(`EquipmentTagConfigInspector`) and the AdminUI editor/validator.

**Fixed namespace** (device-relative; browse-committable from the `/raw` picker without contacting the control):

| Folder | Leaves (type) | Source | Group |
|---|---|---|---|
| `Controller` | `Model`, `NcVersion`, `PlcVersion`, `Options` (String) | `R_VR` (4 or 5 fields; SPLC skipped; empty options preserved) | Slow |
| `Status` | `ExecutionState` (Int32), `ProgramState` (Int32) — raw native enums | `R_RI 23`, `26` | Status |
| `Program` | `Main`, `Current` (String), `Line` (Int64) | `R_RI 24` | Status |
| `Overrides` | `Feed`, `Spindle`, `Rapid` (Float64, percent) | `R_RI 25` (uint32 hundredths) | Status |
| `Axes` | `Names` (String[]), `Positions` (Float64[]) — aligned, controller units | `R_RI 22` | Status |
| `Tool` | `Number` (Int64), `Index`, `AxisCode` (Int32), `Length`, `Radius` (Float64) | `R_RI 51` (8-byte reply ⇒ geometry `BadNotSupported`, never 0) | Slow |
| `Alarms` | `Classes`, `Groups`, `Numbers` (Int32[]), `Messages` (String[]), `Count` (Int32) | `R_RI 27` then `28`; only refusal 57 ends the list | Slow |
| `Timers` | `NcUptime`, `MachineUptime`, `MachineRuntime`, `Spindle0Runtime`, `Spindle1Runtime` (Int64, raw) | `R_RI 30–34`, **disabled by default** | Slow |
| `Capabilities` | one String per feature + `PlcLayout`, `DncLogin`, `DataLogin` | local, never a wire read | Slow |

Array leaves require `"isArray": true` (variable length); the typed editor and browse commit write it. Capability
states: `Unknown`, `Supported`, `Disabled`, `AccessDenied`, `Unsupported`, `InvalidData`, `CommunicationLost` —
evidence about the last read, not a licence assertion.

**PLC bindings** `PLC:<AREA>:<INDEX>` + `dataType`, read via `R_MB`. `INDEX` is an **element** index (1–10 digits,
≤ uint32), multiplied by the native width and added to the region base the control advertises in `R_PR`.
Numeric `R_PR` counts are **byte capacities** (element count = ⌊bytes / width⌋; BYTE/WORD/DWORD share one pool);
the next populated advertised base is a defensive cap. Bit and STRING counts are entries.

| Area | Native | Allowed `dataType` |
|---|---|---|
| `MARKER`, `INPUT`, `OUTPUT`, `COUNTER`, `TIMER` | one byte per Boolean (0/1 only) | Boolean |
| `BYTE` / `WORD` / `DWORD` | signed int8 / int16le / int32le | Int16 (BYTE, WORD only), Int32, Int64 |
| `INPUT_WORD`, `OUTPUT_WORD` | uint16le | Int32, Int64 |
| `STRING` | advertised fixed width, terminated Latin-1 (too wide ⇒ error, never truncated) | String |

Example: `PLC:WORD:4999` → `R_MB` at `base + 4999×2`. Note that `DATA:/PLC/memory/W/9998` uses a native **byte
offset** — the two address spaces differ (see the wire reference).

**DATA bindings** `DATA:<path>` + `dataType` ∈ Boolean/Int16/Int32/Int64/Float64/String, read via `R_DP` under the
opt-in DATA role (`/`→`\`, `"`→`'` normalisation; NUL-free Latin-1; ≤ 242 chars). Value types 2/3/5/8/11/16/17 are
decoded strictly; Boolean accepts `00` and `01`/**`FF`** (FF observed on real iTNC 530 I/O). Coercion never
truncates or wraps — otherwise `BadTypeMismatch`.

At most 256 PLC/DATA bindings per control (excess are skipped and reported on `/hosts`).

## Quality

| Condition | Value status / capability |
|---|---|
| Refusal 22/24 | `BadNotSupported` / `Unsupported` — suppressed for the session |
| Refusal 23/49 | `BadUserAccessDenied` / `AccessDenied` — suppressed for the session, except a provisional denial while the optional DNC login is temporarily failing (retried) |
| Other refusal | `BadUnexpectedError` / `Unknown` — retried next poll |
| Malformed complete record (length, terminator, NaN, duplicate axis, …) | `BadDecodingError` / `InvalidData` |
| Binding type mismatch | `BadTypeMismatch` |
| Out-of-region binding, alarm overflow | `BadOutOfRange` / `InvalidData` (never a truncated list) |
| Disabled feature (telemetry off, timers off, DATA off) | `BadNotSupported` / `Disabled` |
| Unusable optional DNC/DATA credential, or a request the read-only policy refuses | `BadConfigurationError` / `ConfigurationError` — that role's reads only; never sent; the session stays up |
| Not yet acquired | `BadWaitingForInitialData` |
| Transport lost | **every** remote value of that control `BadNoCommunication` at once; capabilities `CommunicationLost` |

There is no cross-poll Good cache: each batch reads the wire; within a batch a shared selector (program,
overrides, axes, tool, the whole alarm walk) and aliased custom addresses are read once.

## Lifecycle, health and comms loss

- **Construction and `InitializeAsync` open nothing.** Acquisition starts on the first `SubscribeAsync` /
  `ReadAsync`, so the `/raw` browse (universal discovery browser, static catalog, `RediscoverPolicy = Once`) never
  opens a session to a production control.
- One background loop per control: connect → INSPECT login → `R_VR` (required) → optional DNC/DATA logins →
  `R_PR` when PLC bindings exist → poll the Status/Custom/Slow groups. Each established session is a new
  **generation**; a batch returning after its session was retired can never overwrite the outage invalidation.
- **Reads are cache-only** (`ReadAsync` never touches the wire); subscriptions push on (value, **status**) change,
  so a control returning with identical readings still re-publishes Good.
- Comms loss → all-value invalidation → bounded exponential reconnect (`Reconnect.*`, clamped to 100 ms–10 min).
  The backoff resets only after a session **published a poll batch** — a control that accepts login + version and
  then drops is backed off, not re-dialled every `InitialDelayMs`. Unlike the Java base, an initial connect
  failure also retries (no manual restart). The loop survives any unexpected fault (logged, retired, backed off);
  JSON-`null` config sections are normalised to defaults by the parser.
- Subscriptions: the initial push and later publications are ordered under one lock, so a subscriber never
  receives an older value after a newer one. A re-init disposes every control loop first; a late start of a
  disposed loop is a no-op.
- **Health:** `Degraded` only while a control's session is down (connect failing / lost), with
  `LastSuccessfulRead` frozen — the conjunction the #527 comms-loss watchdog needs. Per-tag refusals, denials and
  decode errors are quality, not health (else the watchdog would reconnect-loop a control that merely denies one
  selector). The reference's poll-group "partial data" aggregate is on the `/hosts` diagnostics bag
  (`<host:port>.data` = `Good`/`Partial`/`Lost`, plus `.state` and `.model`). Re-initialise tears down every
  session first (#630).

## Test-Connect probe

`HeidenhainDriverProbe` (registered on admin and driver nodes, with the node's `ISecretResolver`) opens a real
session to the first device: INSPECT login + `R_VR`. A bare TCP listener does not read as healthy.

## Tests

- `tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Heidenhain.Tests` — in-process **LSV2 simulator** (`Simulator/`): a
  scripted raw-socket peer for framing tests and a `SimulatedControl` model that records every request and flags
  any non-allowlisted telegram. The Java fixtures' captured iTNC 530 replies (`Fixtures/*.properties`) are replayed
  as golden vectors (inspect-only telemetry on two controls; DATA boundary replies on three).
- `Runtime.Tests/Drivers/HeidenhainDriverEndToEndTests` — the real driver inside `DriverInstanceActor`.
- `Configuration.Tests/DraftValidatorHeidenhainTests`, `AdminUI.Tests/Uns/HeidenhainAuthoringTests` + the fleet
  parity suites.
- **LiveIntegration** (`--filter Category=LiveIntegration`, skipped unless `HEIDENHAIN_LSV2_HOST` is set; optional
  `HEIDENHAIN_LSV2_PORT`, `OTOPCUA_HEIDENHAIN_INSPECT_PASSWORD`): read-only INSPECT identity/selector/layout survey and a
  driver end-to-end status poll. Record its output as .NET commissioning evidence.

## Hardware-gated — not yet proven

No real control was available for this port. Still open:

- **.NET commissioning evidence** on a real control (the LiveIntegration gate) — browse/types/arrays through a
  real OPC UA client, OPC write refusal, network interruption + recovery quality, bounded traffic under load.
- Controller families/versions other than iTNC 530 (TNC 320/430/640) — unproven even in the Java reference.
- Successful raw **`R_MB`** decoding and its Boolean encoding (denied on all four tested controls).
- Physical units of axis positions / tool geometry vs. the HMI; experimental timer semantics (selectors 30–34).
- DNC/DATA permission matrices per control; sustained fleet/load operation.

## Deliberate exclusions

Writes of any kind, file upload/download, remote input/keyboard/motion, parameter edits, PLCDEBUG/MONITOR/FILE
roles, scope setup, arbitrary requests, buffer-size negotiation, vendor SDK, serial transport, built-in SSH,
PLC-wide symbol discovery / memory scanning, OEE mapping, and native alarms as Part 9 conditions (alarms are
published as typed arrays).