LocalNetMsg Agent Guide

LAN instant-messaging desktop app. Stack: Electron 32 + Vue 3 + TypeScript + Vite + Pinia + Element Plus + SQLite (better-sqlite3). Three independent processes built by electron-vite.

Commands

Task	Command
Dev (Electron + HMR)	`npm run dev`
Build (no installer)	`npm run build`
Typecheck main+preload	`npm run typecheck:node`
Typecheck renderer	`npm run typecheck:web`
Typecheck both	`npm run typecheck`
Remote feature self-test (terminal / forward / USB)	`npm run selftest`
Packaged-artifact smoke check (asar unpack + real pty spawn)	`npm run selftest:package` (run after `npm run package:*`)
Windows installer	`npm run package:win` → `dist-Electron\LocalNetMsg-0.1.0-Setup.exe`
macOS / Linux	`npm run package:mac` / `npm run package:linux`
Unpacked dir only	`npm run package:dir`

All package:* scripts bake in ELECTRON_MIRROR + ELECTRON_BUILDER_BINARIES_MIRROR (npmmirror.com). Do not remove unless on the open internet.

npm run selftest runs the remote (terminal / port-forward / USB) self-test: one process, two virtual nodes, real ChatServer + ChatClient + remote managers. See scripts/selftest/.

Verify changes via npm run typecheck + npm run selftest + manual npm run dev.

Layout

src/
  main/       Electron main process (Node) — entry: index.ts
    discovery.ts    UDP broadcast beacon (multi-NIC, per-interface subnet bcast)
    chat-server.ts  WebSocketServer on 0.0.0.0:47900
    chat-client.ts  Outgoing WS with backoff reconnect
    file-server.ts  HTTP /upload + /file, default cap 100GB
    db.ts           SQLite via better-sqlite3 (data/app.db)
    settings.ts     electron-store wrapper (~/AppData/Roaming/local-net-msg/config.json)
    notify.ts       System Notification + Windows overlay badge
    ipc.ts          All ipcMain.handle() wiring
    protocol.ts     MessageEnvelope, WsFrame, DeviceInfo types
  preload/    contextBridge exposing typed API to renderer
  renderer/   Vue 3 SPA (Vite root)
    src/
      main.ts        createApp + Pinia + ElementPlus (full import) + zhCn
      App.vue        Global event listeners (device:*, message:*, settings:*)
      components/    Sidebar, ChatView, MessageInput, MessageItem, SettingsView, MarkdownView
      stores/        Pinia: device.ts, message.ts, session.ts
      api.ts         IPC typings (mirrors preload)
      utils/         format.ts (colorFor, initialsOf, formatSize, ...)
electron.vite.config.ts   Three builds → out/{main,preload,renderer}/

Renderer alias: @ → src/renderer/src.

Network protocol

UDP discovery on 47800, chat WS on 47900, file HTTP on 47901. All three bind 0.0.0.0 and auto-shift on conflict.

DeviceInfo carries address (chosen from the first non-internal IPv4 of the responding NIC) plus chatPort/filePort. The chat server sends no broadcast of its own — discovery comes purely from UDP. Receiver uses rinfo.address (real source IP), never the payload's self.address.

Hard-won pitfalls (don't repeat these)

chat-client MUST have an on('error') listener. Node EventEmitter throws ERR_UNHANDLED_ERROR and kills the main process if 'error' fires with no listener. The WS 'error' event is followed by 'close' which triggers reconnect. Don't try to "fix" by emitting on the client; just console.warn and move on.
Drag-drop file path. Electron 32 removed File.path. Use webUtils.getPathForFile(file) from electron — exposed in src/preload/index.ts as getPathForFile(file). Callers must read it via window.api.getPathForFile(f) BEFORE the await boundary.
Native rebuild. postinstall runs electron-builder install-app-deps to rebuild better-sqlite3 against the bundled Electron ABI. After npm i or upgrading Electron, this must run. If you forget, sqlite open will throw on launch.
mkdir for Windows reserved names. Output dir is dist-Electron\ (escaped; dist\electron chokes on Windows). Don't rename without verifying the build still produces a valid path.
nsis is oneClick: false. Installer asks for install path + creates Desktop/Start-Menu shortcuts. Permissions are user-scoped.
Renderer global drag highlight. Track dragenter/dragleave with a depth counter (not a boolean) — child elements fire leave/enter pairs. See MessageInput.vue's dragDepth.
WS 通道状态要"拉取式"同步, 不能只靠事件推送. 聊天框顶部显示的是"通道可用"（outgoing 或 inbound 任一 WS 活着），跟侧边栏的"设备在线"（UDP 发现）是两回事。启动时主进程往往先连上对端（index.ts 里 connectTo 早于 createMainWindow），那条 device:wsState 事件会在渲染层订阅之前就发出去被丢掉 —— 早期实现只有事件推送，UI 因此永久停在"等待重连…"，而连接其实一直是好的。规矩：(1) device:wsState 推全量快照而不是增量；(2) 渲染层 mount 时主动 invoke('app:state') 拉一次；(3) 渲染层先注册监听再 await，否则 await 期间的事件也会丢。详见 docs/connection-status.md。
File conflict naming. Append _N before the first .: archive.tar.gz → archive_1.tar.gz, .bashrc → .bashrc_1. Logic in file-server.ts targetPath().

Configuration knobs

LNM_MAX_FILE_SIZE=<bytes> env var overrides the 100 GB default in file-server.ts. Useful for testing the limit path.
deviceName, downloadDir, notifications, autoStart live in ~/AppData/Roaming/local-net-msg/config.json via electron-store. Edit the file directly while dev is stopped.
data/app.db — SQLite DB. DELETE to reset all devices/messages. Auto-migrates on next launch.

Packaging gotcha

release/ contains an app.asar Windows cannot delete while the previous app instance holds a file handle. Build now writes to dist-Electron\ to dodge this. If you ever switch back, kill the running app first or you'll get EPERM.

Linux packaging (icon + taskbar)

Ubuntu 装完"没图标"是个坑，有两个独立原因：

linux.icon 必须指向目录，不能是单张 PNG。 electron-builder 把图标装进 /usr/share/icons/hicolor/<size>x<size>/apps/<exe>.png，而单张 PNG 交给 app-builder 时它解析不出尺寸（返回 size: 0），于是装进 hicolor/0x0/ 这种非法目录，桌面环境根本找不到 → 启动器没图标。正确做法是给一个目录，里面按 <size>x<size>.png 命名：resources/icons/{16,24,32,48,64,128,256,512}x{...}.png，然后 linux.icon = "resources/icons"。图标集用 node scripts/make-icon.js 生成（需要 ImageMagick 的 convert；生成结果已提交，平时不用跑）。
StartupWMClass 要跟窗口真实的 WM_CLASS 一致。 electron-builder 默认填 productName（LocalNetMsg），但 Electron 实际设的是可执行文件名（local-net-msg）—— 对不上，任务栏就找不到对应启动器，显示成通用图标。用 xprop -id <wid> WM_CLASS 确认真实值，然后在 build.linux.desktop.StartupWMClass 里写它。

Windows / macOS 仍用单张 resources/icon.png（那里不按尺寸分目录）。

Windows 兼容性

完整的分析、已修问题和待验证清单见 docs/windows-compat.md。最容易踩的两个：

build.asarUnpack 里的原生模块规则必须递归（**/*）。 node-pty 1.2 是"主包 + 平台包"拆包架构，平台包 @lydell/node-pty-<platform>-<arch> 里除了 .node 还有 conpty.dll / OpenConsole.exe，而 node-pty 的 ConPTY worker 用 worker_threads.Worker 起脚本——都必须是磁盘上的真实文件。规则写成 .../node-pty-*/*（单层）会把 prebuilds/<plat>/ 下的东西留在 asar 里，Windows 终端直接起不来（Linux 上看不出来，因为只需要一个 .node）。自测 S7 守着这条规则。
Windows 保留设备名：CON PRN AUX NUL COM1-9 LPT1-9（带扩展名也算）不能直接当文件名——对它们 open() 打开的是设备不是文件。落盘前统一走 src/main/safe-name.ts 的 safeFileName()（按本机平台决定要不要改写，Linux 上 CON 是合法文件名，不该动）。

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