Joseph Doherty
72be19225d
MqttDriver implemented no IWritable, so every MQTT node materialized read-only
regardless of what the operator authored. It now publishes.
Plain -> the tag's writeTopic; UTF-8 text (Raw/Scalar) or a bare JSON
literal (Json)
Sparkplug -> DCMD for a device metric, NCMD for an edge-node metric, carrying
the metric BY NAME with an explicit Datatype and no seq
Both at QoS 0, retain:false. Retain is deliberately not configurable — a retained
command is replayed by the broker on every future subscribe, including the
device's own reconnect, so one stale write would be re-applied forever.
writeTopic is a new, separate TagConfig key, and its ABSENCE is meaningful: the
write is refused BadNotWritable and the node is discovered ViewOnly. The issue's
"do not skip" warning drove the design — the one outcome worse than read-only
nodes is a node that looks writable, returns Good and publishes nothing. Reusing
the read topic would be worse still: it would echo back and read as a confirmed
device value. Browse-time writability is computed by the SAME encoder the write
path uses, so a node cannot advertise writability it would then refuse.
Good means published, not applied — MQTT has no application-level write ack, so
this is Galaxy's optimistic-Good posture and inherits its property: a failed
DEVICE write can never be surfaced. A failed PUBLISH is reported Bad; the
optimism covers what the device did with the command, never whether it was sent.
WriteIdempotent stays default-off.
The encoder is pure and lives in .Contracts, so both wire shapes are testable
without a broker. Unrepresentable values and types with no Sparkplug encoding are
refused rather than coerced — a Reference must not silently become a String on
the wire, and "not-a-number" must not become 0 on a live plant.
LIVE GATE PASSED against the real Mosquitto fixture on 10.100.0.35: 21/21
integration tests, including 6 new ones that observe the published message with
an INDEPENDENT broker subscriber — a fake asserting "publish was called" could
not tell the feature working from the feature publishing to the wrong topic.
The gate earned its keep: the NCMD test initially failed because NCMD is a SHARED
channel — the driver publishes its own rebirth request (Node Control/Rebirth) on
the very topic an edge-node metric write uses, and it arrived first. Correct
driver behaviour, wrong test; the watcher now matches on metric name. Documented,
because anything consuming that topic needs to know. DCMD has no contention.
Offline: 24 encoder + 9 driver tests. The four new status constants are NAMED so
StatusCodeParityTests can see them (#497/#519) — it went 258 -> 262 and validated
each against the pinned SDK.
Also corrects the Mqtt.md "Known gaps" table: prunes the six rows closed in this
round, and fixes the #507 row, which still described rediscovery as inert after
that issue was closed as superseded and its injection path deleted.
Claude-Session: https://claude.ai/code/session_015p7wGqy3YpZNCpDzTpGMKo
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.