FileSync

A ground-up rebuild of how FileSync connects and saves files — native WebRTC, a built-in signaling server, and true streaming-to-disk for transfers of any size.

This is a major release. FileSync no longer depends on PeerJS: connection setup is now handled by a lightweight first-party signaling server bundled with the app, and received files stream straight to disk so even multi-gigabyte transfers stay memory-safe.

[!IMPORTANT]
Upgrading from 3.x requires re-downloading the compose files (docker-compose.yml, and for HTTPS the docker-compose-ssl.yml + Caddyfile). Pulling the new image alone is not enough — see Upgrading.

✨ Highlights

• 🔗 Native WebRTC — PeerJS is gone. Smaller footprint, fewer moving parts, no third-party connection broker.
• 📡 Built-in signaling server — served by FileSync itself at /ws. Nothing extra to run; it relays only connection setup and never sees your files.
• 💾 Streaming downloads, any size — files are written to disk as they arrive, so memory stays flat even on multi-GB transfers.
• 🩺 Redesigned diagnostics page at /test.html — light/dark, an at-a-glance verdict, and a one-click connectivity report to share with support.
• 🛡️ Hardened for production — required secret at startup, rate-limited credentials, a self-healing container, and self-hosted fonts.

🚀 What's new

Connectivity

• Native RTCPeerConnection / RTCDataChannel client replacing the PeerJS wrapper.
• First-party WebSocket signaling relay (/ws) with rate limiting, idle timeouts, and capacity guards.
• Relayed transfers now work correctly behind Docker — TURN relay candidates are rewritten in transit so peers on different networks get a reachable address.

Transfers

• Chunked, backpressured protocol that keeps both sender and receiver memory bounded.
• Three save methods, auto-selected per browser:
  | Method | When | Notes |
  |---|---|---|
  | File System Access | Desktop Chrome/Edge/Brave/Opera (HTTPS) | Streams straight to a file you pick |
  | Service Worker | All modern browsers (HTTPS) | Streamed browser download, memory-safe |
  | Blob | Fallback / plain HTTP | Buffered in memory (~500 MB practical limit) |

Reliability

• Serialized disk writes — fixes a File System Access corruption case on fast/large transfers.
• Transfers no longer hang if a peer drops mid-send; abort, remove, and "cancel all" now tear down cleanly (no leaked connections or stuck downloads).
• Transient network blips are tolerated instead of killing an in-progress transfer.
• The container self-heals: if the backend process dies, it restarts instead of serving a half-dead app.

Security

• The server refuses to start without SECRET_KEY (used to sign TURN credentials and tokens).
• /api/credentials is rate-limited; CORS is off by default (opt-in via CORS_ORIGINS).
• Fonts are self-hosted — no third-party font CDN, satisfying the app's strict Content-Security-Policy.

Tooling & docs

• End-to-end Playwright test harness covering browsers × save methods × connection modes.
• Dependabot for Python, Docker, GitHub Actions, and the test harness.
• README refreshed: how connections are made, the required ports, and how files are saved.

⚠️ Upgrading from 3.x

The compose files changed — re-download them.

1. Re-download the deploy file(s) for your setup:

   • HTTP → deploy/docker-compose.yml
   • HTTPS → deploy/docker-compose-ssl.yml + deploy/Caddyfile

2. Set your secret (now required — the app won't start without it). Generate one:

   python3 -c "import secrets, base64; print(base64.b64encode(secrets.token_bytes(32)).decode())"
   

   Replace both <SECRET_KEY> placeholders in the compose file.

3. Open the required ports (below) if you haven't already.

4. Pull and restart:

   docker compose pull && docker compose up -d
   

💡 No separate PeerJS server is needed anymore — if you ran one, you can decommission it.

📋 Required ports

| Port | Protocol | Purpose |
|---|---|---|
| 80 / 443 | TCP | Web interface (HTTP / HTTPS) |
| 3478 | TCP + UDP | STUN/TURN — connection setup |
| 50000–50100 | UDP | TURN relay range (used when a direct path isn't possible) |

Full changelog: https://github.com/polius/filesync/compare/v.3.7.0...v.4.0.0