LANChat

A cross-platform, no-registration LAN chat app with file transfer support.

📖 中文文档

Features

• 🚀 No Registration - Auto-generates random usernames; click to change anytime
• 💻 Cross-Platform - Linux desktop, Windows desktop, Android App, Web
• 🔍 Auto Discovery - UDP broadcast/multicast based LAN device discovery
• 🔗 Manual Discovery - Add by IP, domain, or hostname; works across VLANs / WireGuard
• 🔄 Smart Reply - Auto-replies to heartbeats; only one side needs to add the other for mutual discovery
• 💬 Real-time Chat - Text messages, streaming messages, and file transfer
• 📁 File Transfer - Large file chunked transfer with configurable auto-accept
• 📸 Image Preview - Automatic preview for image messages
• 💾 History - SQLite database for chat history
• 🔧 Port Config - Customizable service port in settings, overridable via CLI
• 📂 Database Path - Custom database location, persisted in config file
• 🌐 Web Client - Deployable on headless servers
• 🔔 System Notifications - Linux desktop, Windows desktop, Android App, Web
• 💡 Tray Icon Flash - Click to jump to latest unread; right-click menu to toggle notifications
• 🌍 i18n - Automatic system language detection, manual switch, tray menu hot-reload
• 🤖 LANClaw AI Bot - Pi-powered AI chatbot with auto-reply, file analysis, and scheduled tasks
• 📱 Android Dual-Track File Engine — SAF persistable permissions + Share Intent FD cache zero-copy dual track
• 📁 SAF File Picker — Android native ACTION_OPEN_DOCUMENT; selected files remain readable across process/reboot
• 🔁 Offline Re-send — Offline messages auto-cached; auto-re-send on reconnect, including files
• 🔗 Manual Receive - Turn off Auto Download and click to download files manually

Quick Start

AUR

paru -S lanchat-bin

Releases

https://github.com/cap153/LANChat/releases

Build from Source

Prerequisites:

https://v2.tauri.app/start/prerequisites/

# Desktop Linux
cargo tauri build --bundles deb
cargo tauri build --bundles rpm

# Android APK
cargo tauri android build --target aarch64
./sign-apk.sh

# Windows desktop
cd src-tauri
cargo xwin build --release --bin lanchat --target x86_64-pc-windows-msvc

# Web (lightweight, no GUI dependencies)
cd src-tauri
cargo build --release --bin lanchat-web --features web --no-default-features
cargo build --no-default-features --features web --release --target x86_64-pc-windows-gnu # Windows web

Or use the Makefile for one-click builds:

make all          # Build all tested platforms
make deb          # Linux .deb
make rpm          # Linux .rpm
make apk          # Android APK (auto-signed)
make windows-desktop  # Windows desktop (requires cargo-xwin)
make web          # Web (Linux)
make web-windows  # Web (Windows)
make help         # Show help

Running

1. Start the service (default port 8888, configurable in settings):

# Desktop
lanchat

# Web
lanchat-web

CLI arguments --port and --db-path override config file settings with highest priority.

# Web / Desktop
lanchat --port 8889 --db-path /custom/path/lanchat.db

Tip

Run multiple instances by specifying different ports and database paths.
Use the Add panel with <IP>:<port> to discover across ports.
Once one side receives a heartbeat, the reply mechanism enables mutual discovery.

2. Firewall configuration (ufw example):

Important

Ensure both TCP and UDP are allowed for the configured port.

# TCP: Web pages and WebSocket communication
sudo ufw allow 8888/tcp
# UDP: Device discovery (broadcast/multicast/heartbeat)
sudo ufw allow 8888/udp

Custom Themes

Place custom .css files in the config directory (any filename):

• Linux: ~/.config/lanchat/
• Windows: %APPDATA%\.config\lanchat

See built-in themes for reference: https://github.com/cap153/LANChat/tree/main/src/css

Config File

Port, language, and other settings are stored in config.json. CLI arguments --port and --db-path take highest priority.

• Linux: ~/.config/lanchat/config.json
• Windows: %APPDATA%\lanchat\config.json
• macOS: ~/Library/Application Support/lanchat/config.json

Example content:

{
  "db_path": null,
  "port": 8888,
  "lang": "en"
}

Field	Description
db_path	Database path; null = default
port	Listening port, default 8888
lang	Interface language: zh (Chinese), en (English)

Database

Desktop and Web share the same database:

• Linux: ~/.local/share/com.lanchat.app/lanchat.db
• Windows: %APPDATA%\com.lanchat.app\lanchat.db

The database path can be changed in settings (requires restart). The path is stored in ~/.config/lanchat/config.json.

Feature Status

✅ Done

• Auto-generated random usernames
• Click username to rename
• LAN device discovery (UDP broadcast/multicast)
• Real-time online user list
• Standalone Web deployment
• Shared database between desktop and Web
• Settings panel (port, db path, download path)
• Chat history query
• Theme switching
• Android support
• Text message transfer
• File transfer
• Windows support
• Single instance lock
• Streaming file transfer
• Dynamic chunk size based on system memory
• Broadcast and multicast support
• Android hotspot random subnet brute-force
• Web: click file message to download directly
• Desktop: click file message to open containing folder
• Android: receive shared files from other apps and send
• Android: share file messages to other apps
• Desktop & Web: drag-and-drop file sending
• Desktop: paste file sending (zero-copy, Wayland-first)
• Web: paste file sending
• Auto image preview
• Red dot for unread messages
• Lazy-load history (scroll to trigger)
• Delete chat history
• Android: open file messages
• Smart file deduplication (reuse identical files, auto-rename on conflict)
• Offline message re-send on reconnect
• Clipboard image paste sending
• Delete offline users
• Clear chat history
• Android: status bar / navigation bar adaptation
• LANClaw streaming AI replies
• Model switching command (/model)
• New session command (/new)
• Manual discovery (IP / domain / hostname, cross-VLAN / WireGuard)
• UDP heartbeat auto-reply (cross-port / cross-subnet auto discovery)
• System notifications (desktop: PowerShell / notify-send, Web: Notification API, Android: native)
• Tray icon flash (unread notification, click to jump to latest)
• Notification toggle (tray right-click menu, desktop only)
• Manual file receive
• Android SAF persistable permissions + zero-copy FD cache dual-track
• Android SAF native file picker (ACTION_OPEN_DOCUMENT + takePersistableUriPermission)
• Real-time file transfer speed display
• Platform-standard config paths (Linux ~/.config/, Windows %APPDATA%)
• i18n (auto-detect + manual switch + tray hot-reload)

🚧 In Progress

• Group chat
• Better default icon

Project Structure

LANChat/
├── src/                      # Frontend
│   ├── css/
│   │   ├── style.css        # Main stylesheet
│   │   └── vscode.css       # VSCode theme
│   ├── js/
│   │   ├── api.js           # API wrapper (Tauri + HTTP dual backend)
│   │   ├── app.js           # App logic
│   │   └── ui.js            # UI interactions
│   └── index.html           # Main page
├── src-tauri/               # Backend (desktop + Web)
│   ├── src/
│   │   ├── main.rs          # Desktop Tauri entry
│   │   ├── server_main.rs   # Web standalone entry
│   │   ├── lib.rs           # Android entry
│   │   ├── commands.rs      # Tauri commands
│   │   ├── web_server.rs    # HTTP/WebSocket server
│   │   ├── db.rs            # SQLite database logic
│   │   ├── config_file.rs   # Config file read/write
│   │   ├── peers.rs         # Online user manager
│   │   ├── models.rs        # Data models
│   │   ├── utils.rs         # Utilities
│   │   └── network/         # Network module
│   │       ├── discovery.rs # UDP device discovery
│   │       └── messaging.rs # WebSocket messaging
│   ├── capabilities/        # Tauri capability config
│   ├── permissions/         # Custom command permissions
│   └── Cargo.toml
├── Makefile                 # One-click build
└── README.md                # This file

File Status Reference

Role	Status Value	Display Text
Sender	status: "pending"	pending
Sender	file_status: "offering"	offering
Sender	file_status: "uploading"	xx MB/s
Sender	file_status: "sent"	(empty)
Receiver	file_status: "offered"	offered
Receiver	file_status: "invalid"	invalid
Receiver	file_status: "downloading"	xx MB/s
Receiver	file_status: "accepted"	(empty)

Troubleshooting

Windows: missing VCRUNTIME140.dll / VCRUNTIME140_1.dll:
https://aka.ms/vs/17/release/vc_redist.x64.exe
https://aka.ms/vs/17/release/vc_redist.x86.exe

Windows: WebView2 not installed:
https://developer.microsoft.com/en-us/microsoft-edge/webview2

Online user sends messages but they show as Pending on my side:
Disable mobile data / VPN and reconnect to WiFi.

NVIDIA graphics card not rendering correctly on Linux desktop:
Add the environment variable Exec=env __NV_DISABLE_EXPLICIT_SYNC=1 lanchat to the desktop file.

Cross-VLAN / WireGuard:
When devices are on different VLANs or connected via WireGuard, UDP broadcast won't cross subnets. Solution: use the Add panel to enter the peer's IP/domain/hostname with port. The system sends unicast heartbeats periodically (DNS resolution supported, 60s cache).

Tip

Only one side needs to add the other. Upon receiving a heartbeat, the peer auto-replies with its own heartbeat, enabling mutual discovery without manual setup on both sides. Reply heartbeats include a |1 marker to prevent infinite loops.

Tech Stack

• Backend: Rust + Tauri 2.0
• Frontend: Vanilla HTML + CSS + JavaScript
• Database: SQLite (sqlx)
• Network: UDP broadcast/multicast + TCP/WebSocket + HTTP chunked upload
• Web Server: Axum
• AI Bot: LANClaw (separate process, driven by Pi RPC)

License

MIT License

Acknowledgements

• Tauri - Cross-platform app framework
• Axum - Web framework
• SQLx - Async SQL toolkit

Sponsor

If you find this project helpful, feel free to buy me a coffee ☕️

Click to reveal QR code (WeChat Pay)

Your support is greatly appreciated!