Joseph Doherty
e4e313cf1c
SequenceTracker (Driver.Mqtt/Sparkplug/) holds one edge node's Sparkplug stream-continuity state -- design doc SS3.6 invariant #3. Two independent halves: the wrapping 0-255 seq counter that reports whether a message was missed, and the bdSeq session token that ties an NDEATH to the NBIRTH it belongs to. Next-expected is (last + 1) & 0xFF, so 255 -> 0 is the sequence continuing. The boundary is the whole task because it fails differently in each direction: read the wrap as a gap and every edge node is asked to rebirth once per 256 messages, so a busy node spends its life republishing births instead of data; miss a real gap and the driver serves values it knows are behind the device, at Good quality, indefinitely. Both directions are asserted, plus two full wrap cycles so an off-by-one that only misfires at one value has nowhere to hide. A gap is reported once and the tracker then resynchronizes onto the observed value -- holding the baseline at the pre-gap number would make every following message report a gap too, so one lost message would become a permanent rebirth storm, the same pathology as a wrong wrap reached by a different route. An out-of-range seq is refused, never masked. The codec hands seq over as a ulong precisely so a spec-violating publisher's value is not truncated into a plausible-looking one, and masking would finish the job it declined to do: with the baseline at 255, a seq of 256 masks to 0 -- exactly what the wrap expects next -- and the bogus message would be accepted as contiguous. Refused values do not become the baseline either, so the next genuine message is still measured against the last credible one. A birth restarts the sequence via AcceptBirth rather than Accept, so it is never itself a gap; a gap after a birth is still detected. An in-range but non-zero birth seq is adopted rather than refused -- refusing it would demand a fresh rebirth for every message from an otherwise-followable publisher. The first message on a virgin tracker cannot be a gap (nothing to measure it against) but leaves IsBirthSynchronized false, which is how Task 21 tells a mid-stream late join from a synchronized node. bdSeq exists to stop a late Last Will from killing a live node: a node's connection drops, it reconnects and publishes a fresh NBIRTH, and only then does the broker notice the old connection died and deliver its will carrying the PREVIOUS session's bdSeq. Without the compare that stale NDEATH drives every tag of a freshly-born healthy node to Bad. Unknowns fail toward stale deliberately -- only a positive mismatch of two known tokens discards a death, because acting on a death wrongly self-corrects at the next birth (invariant #4) while ignoring a real one leaves a dead node's values flowing Good forever. bdSeq is not a top-level field, so TryReadBdSeq extracts it from the metric named bdSeq and runs it through ReinterpretSigned first: read raw, a negative Int64 bdSeq becomes an enormous ulong -- a plausible-looking session token minted out of nonsense. Falsifiability verified, each mutation reverted after observing RED: (a) no-wrap expected -> 2 RED; (b) Accept always true -> 5 RED; (c) bdSeq compare always matches -> 2 RED; (d) mask out-of-range seq into range -> 2 RED. 28 tests, 437/437 for the MQTT suite. Claude-Session: https://claude.ai/code/session_01GASWkNEi68FSCtvr6rLoEW
OtOpcUa
OPC UA server (.NET 10 AnyCPU) that exposes a fleet of industrial drivers as a single OPC UA address space. Drivers ship in-process for AVEVA System Platform Galaxy (via the sibling mxaccessgw repo), Modbus TCP, Siemens S7, Allen-Bradley CIP (ControlLogix / CompactLogix), Allen-Bradley Legacy (SLC 500 / MicroLogix), Beckhoff TwinCAT (ADS), FANUC FOCAS, OPC UA Client (gateway), and MQTT (broker subscribe; Sparkplug B in progress).
A cross-platform client stack (.NET 10) — shared library, CLI, and Avalonia desktop app — connects to any OPC UA server.
Architecture
OPC UA Clients (CLI, Desktop UI, 3rd-party)
|
v
+-------------------------------------+
| OtOpcUa.Server (.NET 10 AnyCPU) |
| address space + capability fan-out|
+-------------------------------------+
| | | | | | | |
Galaxy Modbus S7 AbCip AbLeg TwinCAT FOCAS OpcUaClient MQTT
|
v
mxaccessgw (sibling repo, gRPC)
|
v
MXAccess COM (x86 worker, on AVEVA box)
Galaxy is the only driver with an external runtime: it speaks gRPC to a separately installed mxaccessgw server (sibling repo at c:\Users\dohertj2\Desktop\mxaccessgw\) which owns the MXAccess COM apartment and the x86/STA bitness constraint server-side. Everything in this repo is platform-agnostic .NET 10.
Prerequisites
- .NET 10 SDK (server, drivers, clients all target .NET 10)
- SQL Server reachable for the central config DB
- For Galaxy specifically: a running
mxaccessgwdeployment — see docs/v2/Galaxy.ParityRig.md - For historian read-back / alarm history / continuous historization: a running
ZB.MOM.WW.HistorianGatewaydeployment (the sole historian backend; consumed as theZB.MOM.WW.HistorianGateway.ClientgRPC package). It must runRuntimeDb:Enabled=true+RuntimeDb:EventReadsEnabled=true, and the API key must carryhistorian:read+historian:write+historian:tags:writescopes.
Quick Start
dotnet restore ZB.MOM.WW.OtOpcUa.slnx
dotnet build ZB.MOM.WW.OtOpcUa.slnx
dotnet test ZB.MOM.WW.OtOpcUa.slnx
# Run the server in dev (foreground)
dotnet run --project src/Server/ZB.MOM.WW.OtOpcUa.Host
The server starts on opc.tcp://localhost:4840 with the None security profile. Configure Security.Profiles in src/Server/ZB.MOM.WW.OtOpcUa.Host/appsettings.json to enable Basic256Sha256-Sign or Basic256Sha256-SignAndEncrypt. See docs/security.md.
Install as Windows Services
Production deployment is driven by scripts/install/Install-Services.ps1, which registers the OtOpcUa server service under a chosen service account. Historian support requires a separately deployed ZB.MOM.WW.HistorianGateway and Galaxy support a separately installed mxaccessgw — neither this repo nor the install script provisions them.
.\scripts\install\Install-Services.ps1 `
-InstallRoot 'C:\Program Files\OtOpcUa' `
-ServiceAccount 'DOMAIN\svc-otopcua'
The historian backend is the external ZB.MOM.WW.HistorianGateway (not installed by this script). See the script header and docs/ServiceHosting.md for full options.
Client CLI
dotnet run --project src/Client/ZB.MOM.WW.OtOpcUa.Client.CLI -- connect -u opc.tcp://localhost:4840
dotnet run --project src/Client/ZB.MOM.WW.OtOpcUa.Client.CLI -- browse -u opc.tcp://localhost:4840 -r -d 3
dotnet run --project src/Client/ZB.MOM.WW.OtOpcUa.Client.CLI -- read -u opc.tcp://localhost:4840 -n "ns=2;s=SomeNode"
dotnet run --project src/Client/ZB.MOM.WW.OtOpcUa.Client.CLI -- write -u opc.tcp://localhost:4840 -n "ns=2;s=SomeNode" -v 42
dotnet run --project src/Client/ZB.MOM.WW.OtOpcUa.Client.CLI -- subscribe -u opc.tcp://localhost:4840 -n "ns=2;s=SomeNode" -i 500
See docs/Client.CLI.md and docs/Client.UI.md.
Documentation
Architecture deep-dives
| Topic | Doc |
|---|---|
| OPC UA server composition, namespace fan-out, Polly invoker | docs/OpcUaServer.md |
| Address space layout | docs/AddressSpace.md |
| Read / Write dispatch (driver vs virtual vs scripted-alarm) | docs/ReadWriteOperations.md |
| Incremental sync (driver-backend rediscovery + config publishes) | docs/IncrementalSync.md |
| Service hosting (Server + Admin; external HistorianGateway backend) | docs/ServiceHosting.md |
| Security (transport, LDAP, certificates) | docs/security.md |
| Redundancy | docs/Redundancy.md |
| Status dashboard | docs/StatusDashboard.md |
Drivers
| Topic | Doc |
|---|---|
| Driver specs (per-driver capability surface, config, addressing) | docs/v2/driver-specs.md |
| Galaxy driver | docs/drivers/Galaxy.md |
| Modbus / S7 / AbCip / AbLegacy / TwinCAT / FOCAS / OpcUaClient / MQTT | docs/drivers/ |
| Galaxy parity rig (mxaccessgw setup) | docs/v2/Galaxy.ParityRig.md |
| Galaxy performance + tracing | docs/v2/Galaxy.Performance.md |
Clients
| Topic | Doc |
|---|---|
| Client CLI | docs/Client.CLI.md |
| Client UI (Avalonia desktop) | docs/Client.UI.md |
v1 archive
The original v1 in-process MXAccess docs (Galaxy.Host topology, Configuration env vars, AlarmTracking, DataTypeMapping, HistoricalDataAccess, Subscriptions, etc.) are preserved under docs/v1/ — historical reference only. PR 7.2 retired the v1 architecture on 2026-04-30; current state is documented in the sections above.
License
Internal use only.