Beam

Beam: LAN File Transfer

Fast, frictionless file transfer for your local network. Send files, text, and messages between computers on the same WiFi with zero setup.

Built with Tauri 2 + React 18 | License: MIT

Users need a simple, instant way to transfer files between devices on the same network without:

• Cloud upload/download overhead
• Complex setup or pairing rituals
• Dependency on internet connectivity
• Loss of privacy to third-party servers

The friction of traditional file transfer methods (email, cloud storage, USB drives) for local LAN scenarios.

Beam — a cross-platform desktop application that enables instant peer-to-peer file transfer over local networks.

Why it works:

• Automatic discovery via mDNS: devices announce themselves, no manual IP entry
• Direct TCP streaming between peers on the same subnet: no intermediary servers
• Integrity verification with SHA-256 hashing on both ends
• Smart compression for batches of files (auto-zip, auto-unzip)
• Bandwidth control to prevent network congestion
• Background operation via system tray, accepts transfers while minimized
• Cross-platform native builds for Windows, macOS, Linux

Result: drag files → pick device → send. That's it. Receivers see sender name, file list, and optional note before accepting.

Frontend Stack:

• React 18 + TypeScript
• Tailwind CSS (styling)
• Zustand (state management)
• Framer Motion (animations)
• Lucide icons

Backend Stack:

• Tauri 2 (cross-platform desktop framework)
• Rust + Tokio (async runtime)
• SHA2 (integrity hashing)
• Rayon (parallel hashing across CPU cores)
• Zip v2 (compression/decompression)

Networking:

• mDNS (mdns-sd) for peer discovery on _beam._tcp
• TCP with length-framed JSON protocol
• Custom Offer → Response → streaming protocol

System Integration:

• System tray icon (minimize to background)
• File explorer integration
• Watch folder monitoring (Notify crate)
• Auto-update from GitHub releases
• Native window vibrancy (Windows Mica blur)

Data Persistence:

• settings.json: bandwidth limits, device groups, trusted devices
• Transfer history log
• Conflict resolution: rename / overwrite / skip

mDNS Reliability:

• Peer discovery inconsistent across network configurations (subnets, VPNs, WiFi 6)
• Lesson: Added manual fallback + retry logic, clear error messaging for firewall blocks

Parallel Hashing at Scale:

• Computing SHA-256 on thousands of files while UI remains responsive
• Lesson: Rayon threadpool + chunked I/O, UI event debouncing to prevent lag

Cross-Platform Binary Signing:

• Signing Windows MSI, macOS DMG, and Linux AppImage with different cert authorities
• Lesson: GitHub Actions workflow templates, platform-specific signing paths

Bandwidth Throttling Without Blocking:

• Sleeping between chunks blocks the Tokio task
• Lesson: Tokio::time::sleep() is async-safe; measure per-chunk, adjust on the fly

Conflict Handling:

• Files exist at destination: rename (add suffix), overwrite, skip, or ask user
• Lesson: Conflicts are rare on LAN, batch resolve with sensible defaults

UI State During Active Transfers:

• Users drag new files while transfers are in flight
• Lesson: Zustand queue + cancel button per transfer, don't block the sender

Auto-Update Security:

• Public GitHub releases, verifying signatures
• Lesson: Always require HTTPS, validate release checksums, rollback on failure