julian
dbf1fa17d7
Capture hard-won dev knowledge that was only in commit messages: - wsl-dev-networking: WSL2 NAT blocks UDP broadcast (device discovery can't reach the LAN); fix is mirrored networking (.wslconfig, Win11 22H2+), plus the gotchas that remained after — multiple interfaces, subnet-directed broadcast, localhost->IPv6 stall. Alternatives for non-mirrored setups. - local-dev-workflow: first-time setup, pnpm dev, and the gotchas (the strip-types dev-server hang -> tsx, the 127.0.0.1 proxy fix, .env loading, seeding into the right DB). - device-discovery: corrected the old "broadcast permission (EACCES)" note — the real cause was the lib not enabling SO_BROADCAST for global 255.255.255.255; documented the three verified broadcast gotchas + I/O serialization. - schema: add a `reference` page type; new "Dev environment" index section; log. Links lint clean; both new pages well-connected.
67 lines
3.5 KiB
Markdown
67 lines
3.5 KiB
Markdown
---
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type: concept
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tags: [parking, architecture, devices, setup]
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sources: [parking-system-architecture]
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updated: 2026-06-15
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---
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# Device Discovery
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An optional driver capability: **find devices on the LAN** so the admin doesn't have to type
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connection details by hand during [[first-run-setup]]. Modeled generically so any driver can
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opt in.
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> Implementation-derived (from `@parking/devices` + setup API/UI), not the source doc.
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## The capability
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A driver may implement `DiscoverableDriver` — `discover() => DiscoveredDevice[]`. Each found
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device carries an `id`, a `label`, a `config` blob to **auto-fill** the setup form, and `info`
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(firmware, MAC, …). The [[device-registry]]'s `isDiscoverable()` guard lets the system treat it
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as optional; the setup catalog returns a `discoverable` list of driver ids.
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## UHPPOTE discovery
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The [[uhppote-controller]] supports discovery natively: a **UDP broadcast** (`get-devices` on
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port `60000`) that **every controller on the LAN answers** with its serial, IP, netmask, gateway,
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MAC, firmware version, and date. The official `uhppoted` lib exposes this as `getDevices(ctx)`;
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the `uhppote` driver maps each result into a `DiscoveredDevice` (serial → id, IP → host).
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**Verified on real hardware** (serial 225088491).
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### Broadcast gotchas (learned the hard way — see [[wsl-dev-networking]])
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These cost real debugging time; the `uhppote` driver now handles all three:
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1. **Broadcast to the *subnet-directed* address, not the global `255.255.255.255`.** The
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`uhppoted` lib only calls `setBroadcast(true)` when the target matches a **local interface's
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subnet broadcast** (e.g. `10.0.10.255`). For the global address it skips it, so the `send`
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fails with **`EACCES`**. The driver computes the subnet broadcast from `os.networkInterfaces()`.
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2. **A host with multiple interfaces must broadcast on *all* subnets.** With several NICs (LAN,
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VPN/Tailscale, docker bridges) the controller is on only one. Picking the first interface
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misses it; the driver broadcasts on every subnet and dedupes by serial.
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3. **For *unicast* ops (status / open), the lib's `Config` broadcast must match the target's
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subnet** — it governs reply routing, so a mismatched broadcast makes `getStatus` time out even
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though `openDoor` "succeeds". The driver sets the broadcast per the target host's subnet. (This
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was the health-check "offline/timeout" bug: a 5 s timeout dropped to 24 ms once fixed.)
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Also: concurrent `uhppoted` calls collide on the `:60001` reply-listener port (EACCES / dropped
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replies), so the driver **serializes** all controller I/O. Override the broadcast with
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`UHPPOTE_BROADCAST` for unusual setups.
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## Flow
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1. The setup catalog flags `uhppote` as discoverable.
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2. Admin clicks **Scan** → `GET /api/setup/discover/:driverId` (admin-only).
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3. The server runs `discover()` and **health-checks each found device** so the admin sees
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reachability before assigning.
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4. Selecting a result **auto-fills serial + host**; the admin then assigns it to a lane.
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## Deployment notes
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- Discovery is an **L2 broadcast**: the host and controller must share a layer-2 segment. Works
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on the isolated device VLAN ([[network-isolation]]). A routed/NAT'd network (e.g. WSL2 NAT mode
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— see [[wsl-dev-networking]]) blocks it entirely.
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- Discovery shares the same unauthenticated UDP exposure as everything else UHPPOTE — another
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reason the controllers live on an isolated VLAN ([[uhppote-udp-protocol]]).
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- Cameras (Hikvision/Dahua via ONVIF/WS-Discovery) could implement the same interface later.
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