# mbproxy

A .NET 10 Windows Service that sits inline as a Modbus TCP proxy in front of a fleet of AutomationDirect DirectLOGIC DL205/DL260 controllers, rewriting BCD-encoded registers bidirectionally so upstream clients can read and write them as plain integers. Since Phase 11, the proxy also offers an opt-in per-tag response cache (default OFF) for FC03/FC04 reads with bounded operator-configured staleness — see [`docs/design.md`](docs/design.md) → "Response cache (Phase 11)" before enabling it.

## Hard constraints / prerequisites

- **Windows 10 / Server 2019 or later, 64-bit.** No Linux or Docker support — the service uses `Microsoft.Extensions.Hosting.WindowsServices` and the Windows Event Log.
- **Modbus TCP backends reachable** from the proxy host on port 502 (or the port configured per PLC). The H2-ECOM100 module caps simultaneous connections at **4 per PLC** — a fifth upstream client will fail to connect.
- **Admin rights** to install the service (`install.ps1` requires elevation).
- **No COM dependency** — this is a pure .NET 10 socket-level proxy (unlike the `.NET Framework 4.8 / x86` siblings in this repo).
- **Python 3.10+** on the test machine to run the pymodbus-backed E2E simulator (not needed to run the service in production).

## Layout

```
src/Mbproxy/          Main C# project (net10.0, Microsoft.NET.Sdk.Worker)
tests/Mbproxy.Tests/  xUnit v3 test project (314 unit + 48 E2E tests)
install/              PowerShell install/uninstall scripts and config template
docs/                 Design document, phase plans, and operations runbook
DL260/                DL205/DL260 reference material and pymodbus simulator profile
```

## Resource index

| Task | Go to |
|---|---|
| Full architecture, schema, log events, status counters, test strategy | [`docs/design.md`](docs/design.md) |
| Phase-by-phase implementation plan | [`docs/plan/README.md`](docs/plan/README.md) |
| Install, upgrade, config, logs, troubleshooting | [`docs/operations.md`](docs/operations.md) |
| DL205/DL260 Modbus quirks (BCD, CDAB, octal V-memory, FC limits) | [`DL260/dl205.md`](DL260/dl205.md) |
| pymodbus simulator profile (register seeds for E2E tests) | [`DL260/dl205.json`](DL260/dl205.json) |
| Agent-oriented coding guide (architecture bullets, device quirks, phase context) | [`CLAUDE.md`](CLAUDE.md) |

## Build and run

**Build (Debug, multi-file — fast for iteration):**

```powershell
dotnet build Mbproxy.slnx -c Debug
```

**Publish (Release, single-file self-contained, win-x64):**

```powershell
dotnet publish src/Mbproxy/Mbproxy.csproj -c Release -r win-x64 --self-contained true -o C:\build\mbproxy-publish
```

The published output is a single `Mbproxy.exe` (~100 MB). The self-contained publish bundles the full .NET 10 + ASP.NET Core runtime. No .NET installation is required on the target machine.

**Run tests:**

```powershell
dotnet test Mbproxy.slnx -c Debug                    # all tests
dotnet test Mbproxy.slnx -c Debug --filter Category=Unit   # unit tests only (no Python required)
dotnet test Mbproxy.slnx -c Debug --filter Category=E2E    # E2E tests (require Python + pymodbus)
```

**Run interactively (without installing as a service):**

```powershell
cd src/Mbproxy
dotnet run --configuration Debug
```

Edit `src/Mbproxy/appsettings.json` to configure PLCs before running. The admin status page will be at `http://localhost:8080/` by default.

## Install

Full detail is in [`docs/operations.md`](docs/operations.md). Quick path:

```powershell
# 1. Publish
dotnet publish src/Mbproxy/Mbproxy.csproj -c Release -r win-x64 --self-contained true -o C:\build\mbproxy-publish

# 2. Install (elevated PowerShell)
.\install\install.ps1 -PublishOutput C:\build\mbproxy-publish -Start

# 3. Edit the config that was placed at %ProgramData%\mbproxy\appsettings.json

# 4. Verify
Invoke-WebRequest http://localhost:8080/ -UseBasicParsing
```

## Maintenance

Documentation doctrine for this repo: [`../DOCS-GUIDE.md`](../DOCS-GUIDE.md).

- This README routes to deep docs — it does not duplicate them.
- Design decisions: [`docs/design.md`](docs/design.md) is the source of truth.
- When the service's public surface or task→tool mapping changes, update this README and the root [`../CLAUDE.md`](../CLAUDE.md) index row.