docs(phase5): real Test-Connect handshakes per driver + degrade semantics
Create docs/drivers/TestConnectProbes.md: full reference for the Phase 5 protocol-handshake probes — result contract, per-driver handshake table, TwinCAT/FOCAS/Galaxy degrade semantics, live-verify scope, and the Historian.Wonderware already-done note. Annotate the Phase 7 step in docs/plans/2026-05-28-adminui-driver-pages-design.md with a shipped note pointing at the phase-5 design doc and TestConnectProbes.md.
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Joseph Doherty
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# Test-Connect Probes — Protocol Handshakes
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Each driver's **Test-Connect** button in the AdminUI runs a probe against the
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form's current config (never the persisted row, never the live driver actor).
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Before Phase 5 (shipped 2026-06-16) every probe was a bare TCP `ConnectAsync`
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— a live-but-rejecting device showed a healthy green tick, and the operator
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only discovered the truth when the driver faulted at deploy. Phase 5 replaced
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each TCP-only probe with a **real protocol handshake** so a reachable-but-wrong
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or actively-rejecting endpoint now reads RED.
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The `IDriverProbe` / `DriverProbeResult` contract and DI registration are
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unchanged. Probes run in a transient actor with a timeout clamp of 1–60 s
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and must not mutate any state.
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For the AdminUI probe flow (button → `AdminOperationsActor` → transient probe
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actor), see
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[`docs/plans/2026-05-28-adminui-driver-pages-design.md`](../plans/2026-05-28-adminui-driver-pages-design.md)
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§4.
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---
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## Result contract
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All probes return a consistent `DriverProbeResult(bool Ok, string? Message, TimeSpan? Latency)`.
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The message templates below are uniform across all 8 drivers:
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| Outcome | `Ok` | Message template |
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|---------|------|-----------------|
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| TCP connect fails | `false` | `"Connect failed: {SocketErrorCode}"` |
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| TCP ok + handshake ok | `true` | driver-specific descriptive string (see table below) |
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| TCP ok but handshake rejected | `false` | `"Reachable at {host}:{port} but {proto} handshake failed: {detail}"` |
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| Timeout | `false` | `"Probe timed out after {n}s."` |
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The third row is the key new behavior: a reachable device that answers on the
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port but rejects the protocol-level handshake now surfaces a `false` result
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with a human-readable explanation rather than a false-green TCP-open tick.
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---
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## Per-driver handshake
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| Driver | Handshake | Ok message | Dev-rig target |
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|--------|-----------|------------|----------------|
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| **Modbus** | FC03 (Read Holding Registers, qty 1 @ addr 0) via `ModbusTcpTransport`. A Modbus exception PDU still proves a real Modbus device → `Ok`. A non-MBAP reply → handshake fail. | `"Modbus FC03 OK"` | `10.100.0.35:5020` (Modbus sim) |
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| **OpcUaClient** | `DiscoveryClient.GetEndpointsAsync` — no session, no app-cert, no auth. ≥ 1 endpoint → `Ok`. A non-OPC-UA TCP server throws or times out → handshake fail. | `"OPC UA: N endpoint(s)"` | `opc.tcp://10.100.0.35:50000` (opc-plc) |
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| **S7** | `Plc.OpenAsync` (COTP CR/CC + S7 setup-communication), check `IsConnected`, then `Close`. Wrong rack/slot or a non-S7 server causes `OpenAsync` to throw → handshake fail. | `"S7 connected (CPU …)"` | `10.100.0.35:1102` (python-snap7 sim) |
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| **AbCip** | `libplctag` Tag `InitializeAsync` (EIP session + CIP Forward Open). A CIP-level error such as tag-not-found still proves the controller answered CIP → `Ok`. A session/ForwardOpen/connect error → handshake fail. | `"CIP session OK"` | `10.100.0.35:44818` (CIP sim) |
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| **AbLegacy** | Same `libplctag` `InitializeAsync` handshake as AbCip, PCCC protocol family. | `"CIP session OK"` (PCCC family) | Deferred — no PLC5/SLC sim |
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| **TwinCAT** | `AdsClient.Connect` + `ReadStateAsync`. See [degrade semantics](#twincat-degrade) below. | `"ADS state: {state}"` | Deferred — no ADS target |
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| **FOCAS** | `cnc_allclibhndl3` via FWLIB P/Invoke (`Wire.WireFocasClient`). See [degrade semantics](#focas-degrade) below. | `"FOCAS handle OK"` | Deferred — no CNC + FWLIB |
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| **Galaxy** | gRPC unary call to `GalaxyRepository.TestConnection` on the configured mxaccessgw endpoint. See [auth-rejection rule](#galaxy-auth-rejection) below. | `"gateway gRPC OK"` | `http://10.100.0.48:5120` (mxaccessgw) |
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**Historian.Wonderware** already performed a real handshake (`Hello` → `HelloAck`)
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before Phase 5 and was not changed by this work. See
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[`Historian.Wonderware.md`](Historian.Wonderware.md) for details.
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---
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## Degrade semantics
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Three drivers have environmental constraints that can prevent the handshake
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from running on certain hosts. The **degradation principle** is: the probe
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must never produce a result *worse* than today's TCP-only probe. A genuine
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protocol rejection from a reachable device is a correct RED; an inability to
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*run* the handshake at all (no FWLIB, no managed router) degrades to the
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existing TCP-reachability message — still a green tick but annotated.
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### TwinCAT degrade
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Where the handshake is available:
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- `AdsClient.Connect(netId, port)` + `ReadStateAsync` → `Ok=true`,
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`"ADS state: {state}"` (Run / Config / Stop).
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- An ADS **route-table rejection** from a reachable ADS router is a **true RED**:
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`"Reachable at {host}:{port} but ADS handshake failed: {detail} — check the
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target's ADS route table authorizes this host"`. This is the correct result:
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the driver would also be unable to function without an authorized route.
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Where the handshake is unavailable (headless server, no TwinCAT runtime, the
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managed AMS router cannot start):
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- Probe degrades to TCP-reachability: `Ok=true`,
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`"(ADS handshake unavailable on this host — TCP reachability only)"`.
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### FOCAS degrade
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On a Windows host with the FANUC FWLIB shared library present:
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- `cnc_allclibhndl3` is called via the existing `Wire.WireFocasClient` P/Invoke.
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A successful handle allocation → `Ok=true`, `"FOCAS handle OK"`.
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- A CNC-level rejection → handshake fail.
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On dev, Linux, or macOS (no native FWLIB — `UnimplementedFocasClientFactory`
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gates the driver):
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- `DllNotFoundException` / `NotSupportedException` is caught and the probe
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degrades to TCP-reachability: `Ok=true`,
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`"(FOCAS handshake unavailable on this host — FWLIB absent, TCP reachability only)"`.
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### Galaxy auth-rejection rule
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The probe builds the gRPC channel from the form's config and issues one
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lightweight unary call. It does **not** resolve `secretref:` secrets — the
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key string in the transient config (possibly empty or unresolved) is used as-is.
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- `Unavailable` / transport failure → `Ok=false` (gateway is down or unreachable).
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- `Unauthenticated` / `PermissionDenied` → **`Ok=true`**,
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`"gateway reachable & speaking gRPC; auth not checked"` — an auth rejection
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proves a live mxaccessgw gRPC server. This is the correct result: the driver's
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own session-layer will handle auth; the probe is testing reachability only.
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---
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## Live-verify scope
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| Driver | Live-verify status | Notes |
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|--------|-------------------|-------|
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| Modbus | Verified | Dev-rig sim `10.100.0.35:5020`; green vs sim, RED vs wrong port / non-Modbus server, timeout vs black-hole IP |
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| OpcUaClient | Verified | opc-plc `10.100.0.35:50000`; same three-scenario matrix |
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| S7 | Verified | python-snap7 `10.100.0.35:1102` |
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| AbCip | Verified | CIP sim `10.100.0.35:44818` |
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| Galaxy | Verified | mxaccessgw `10.100.0.48:5120`; `Unauthenticated` reply counts as Ok |
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| AbLegacy | Deferred | No PLC5/SLC sim; unit-proven + code path identical to AbCip |
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| TwinCAT | Deferred | No ADS target; unit-proven + degrade guard tested |
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| FOCAS | Deferred | No CNC + FWLIB on dev host; degrade guard is the CI-observable path |
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---
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## Implementation references
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- Phase 5 design: `docs/plans/2026-06-16-stillpending-phase-5-probes-design.md`
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- Parent roadmap: `docs/plans/2026-06-15-stillpending-backlog-design.md` §Phase 5
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- AdminUI probe flow: `docs/plans/2026-05-28-adminui-driver-pages-design.md` §4
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- Per-driver probe implementations: `src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.<Type>/<Type>DriverProbe.cs`
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- `IDriverProbe` contract: `src/Core/ZB.MOM.WW.OtOpcUa.Core.Abstractions/IDriverProbe.cs`
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- Probe dispatch + timeout clamp: `src/Server/ZB.MOM.WW.OtOpcUa.Host/Actors/AdminOperationsActor.cs` (around line 284)
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