histsdk/README.md

histsdk

Pure managed .NET 10 client for AVEVA Historian's binary WCF protocol. The production SDK has no dependency on aahClientManaged.dll, aahClient.dll, or any other AVEVA native runtime — the wire protocol is reverse-engineered and re-implemented in C#.

Read-only by design. The required surface (per CLAUDE.md):

Operation	Status
ProbeAsync	live-verified
ReadRawAsync	live-verified
ReadAggregateAsync	live-verified (TimeWeightedAverage; other modes need fixtures)
ReadAtTimeAsync	live-verified
ReadEventsAsync	live-verified (typed event + 31-property property bag)
BrowseTagNamesAsync	live-verified
GetTagMetadataAsync	live-verified for 17 distinct native data-type codes
GetConnectionStatusAsync	synthesized from authenticated probe (matches native semantic)
GetStoreForwardStatusAsync	synthesized defaults (no SF sidecar to probe)
GetSystemParameterAsync	live-verified via Stat/GetSystemParameter

Out of scope: write-back, store-forward write, configuration changes.

Quick start

using AVEVA.Historian.Client;
using AVEVA.Historian.Client.Models;

await using HistorianClient client = new(new HistorianClientOptions
{
    Host = "localhost",
    IntegratedSecurity = true,
    Transport = HistorianTransport.LocalPipe,
});

DateTime endUtc   = DateTime.UtcNow;
DateTime startUtc = endUtc - TimeSpan.FromMinutes(10);

await foreach (HistorianSample sample in client.ReadRawAsync(
    "SysTimeSec", startUtc, endUtc, maxValues: 100))
{
    Console.WriteLine($"{sample.TimestampUtc:o}  {sample.NumericValue}  Q={sample.Quality}");
}

For a remote Historian over Net.TCP set Transport = HistorianTransport.RemoteTcpIntegrated and Host to the server hostname. Remote-TCP plumbing exists but only LocalPipe has live verification in this checkout.

Build & test

dotnet build  .\Histsdk.slnx --no-restore
dotnet test   .\Histsdk.slnx --no-build --logger "console;verbosity=minimal"

Run a single test class:

dotnet test .\Histsdk.slnx --no-build --filter "FullyQualifiedName~WcfDataQueryProtocolTests"

Live integration tests (tests/AVEVA.Historian.Client.Tests/HistorianClientIntegrationTests.cs) are gated and skip cleanly without these env vars:

$env:HISTORIAN_HOST       = 'localhost'
$env:HISTORIAN_TEST_TAG   = 'SysTimeSec'      # any tag the server has data for
# Optional for non-integrated auth:
$env:HISTORIAN_USER, $env:HISTORIAN_PASSWORD
$env:HISTORIAN_TAG_FILTER = 'Sys*'             # or any LIKE-pattern

Repository layout

src/AVEVA.Historian.Client/    Production SDK — pure managed .NET 10. No native AVEVA dependency.
tests/                          Unit tests (golden-byte / round-trip) + gated live integration tests.
tools/                          Reverse-engineering tooling (NOT shipped):
  AVEVA.Historian.ReverseEngineering/  .NET 10 CLI: WCF probes, dnlib IL inspection,
                                       IL-rewrite instrumentation (instrument-wcf-{write,read}message,
                                       instrument-openconnection*, instrument-startdataquery, etc.).
  AVEVA.Historian.NativeTraceHarness/  .NET Framework harness that loads aahClientManaged.dll for
                                       byte-for-byte parity testing against the native wrapper.
  AVEVA.Historian.NetFxWcfProbe/       .NET Framework WCF probe for ruling out .NET 10-only differences.
  AVEVA.Historian.ReverseInstrumentation/  Helper assembly injected into IL-rewritten wrapper copies.
  AVEVA.Historian.WcfCaptureServer/    Fake server for endpoint experiments.
scripts/                        PowerShell + Frida runners + Python decoders for capture analysis.
fixtures/protocol/              Sanitized golden-byte fixtures.
docs/reverse-engineering/       Sanitized handoff evidence; commit-safe summaries only.

Native AVEVA binaries (current/, aveva-install-x64/, aveva-install-x86/) are gitignored. Each developer fetches their own copy from the AVEVA installer; we neither modify nor redistribute them.

Documentation

Read in order before non-trivial work:

Doc	Purpose
AGENTS.md	Standing project constraints and safety rules.
CLAUDE.md	Build commands, code architecture, the active protocol blocker (now resolved) and SDK surface.
docs/reverse-engineering/handoff.md	Decision record + decoded protocol evidence (binding shapes, descriptor layouts, Open2 v6 response, event-row wire format, property-bag value encoding).
instructions.md	Original plan + decision record.

Architecture

Three intentionally decoupled subsystems under src/AVEVA.Historian.Client/:

• HistorianClient + HistorianClientOptions — public façade. Validates inputs; delegates reads to Historian2020ProtocolDialect; delegates probe / tag metadata / browse / status helpers to the WCF layer.
• Wcf/ — managed WCF/MDAS layer. Custom MdasMessageEncoder wraps SOAP 1.2 + WS-Addressing 1.0 in AVEVA's application/x-mdas framing. Three binding flavors via HistorianWcfBindingFactory: plain MDAS over Net.NamedPipe (local), MDAS + Windows transport (remote /Hist-Integrated), MDAS + certificate (remote /HistCert). Service contracts in Wcf/Contracts/ mirror the server-side WCF surface (versioned per native interface — IHistoryServiceContract, IRetrievalServiceContract2..4, IStatusServiceContract2, etc.).
• Protocol/ — binary frame layer. Historian2020ProtocolDialect is the version-anchored bridge between the public façade and the WCF + frame layers. Methods without protocol evidence throw ProtocolEvidenceMissingException rather than guessing wire bytes.
• Models/ — public DTOs and enums. HistorianSample, HistorianAggregateSample, HistorianEvent, HistorianTagMetadata, HistorianDataType, RetrievalMode, HistorianTransport, etc.

Read flow end-to-end (live-verified against localhost):

Hist.GetV → Hist.ValCl × N → Hist.Open2 → Retr.GetV → Retr.IsOriginalAllowed →
Retr.StartQuery2 → loop Retr.GetNextQueryResultBuffer2 → typed HistorianSample rows

Event flow end-to-end (live-verified):

Hist.GetV → Hist.ValCl × N → Hist.Open2 → Hist.UpdC3 → 6× Stat.GetSystemParameter →
Hist.RTag2 → Stat.GetSystemParameter(AllowRenameTags) → Trx.GetV → Stat.GetV →
Retr.GetV → Hist.EnsT2(CmEventTagId) → Retr.StartEventQuery →
loop Retr.GetNextEventQueryResultBuffer → typed HistorianEvent rows with
property dictionary → Retr.EndEventQuery → Hist.Close2

Safety

• Production code under src/ must remain pure managed .NET 10 with no native AVEVA reference. Reverse-engineering harnesses under tools/ may reference native binaries.
• Never commit credentials, hostnames, user names, customer tag names, or raw packet captures. *.ndjson, current/, aveva-install-*/, and artifacts/ are gitignored precisely because they accumulate identity-bearing runtime data.
• Methods without protocol evidence throw ProtocolEvidenceMissingException. Do not stub fake behavior — leave them throwing until evidence supports an implementation.

Status

108 unit + live integration tests pass (dotnet test --logger "console;verbosity=minimal"). Full read-only SDK surface verified end-to-end against a local Historian. Remote-TCP transports and explicit-credentials path are wired but await live verification.