DROP

Peer-to-peer file sharing in the browser. No uploads to any server -- files transfer directly between devices using WebRTC.

Same WiFi/network required. All devices must be connected to the same local network (same WiFi router) to discover and transfer files to each other.

How it works

1. A lightweight signaling server introduces peers to each other
2. Peers connect directly via WebRTC DataChannel
3. Files are chunked (16KB) and streamed with backpressure
4. End-to-end crypto handshake (Ed25519 / RSA-PSS fallback)

Quick start

# Install dependencies
npm install

# Start the signaling server (Terminal 1)
npm run server

# Start the web app (Terminal 2)
npm run dev

Open http://localhost:3000 on two devices (or two tabs). Both see each other in the peer list. Click a peer, pick files, send.

Connecting from another device

Access the app via the host machine's IP (e.g. http://192.168.x.x:3000).

Note: WebRTC and Web Crypto API require a secure context. localhost works out of the box. For other IPs, either:

• Use HTTPS (self-signed cert)
• Chrome: enable chrome://flags/#unsafely-treat-insecure-origin-as-secure for that origin

Scripts

Command	Description
npm run dev	Next.js dev server
npm run build	Static export to out/
npm run server	WebSocket signaling server on port 8080
npm start	Serve the static export

Architecture

Browser A ──WS──> Signaling Server <──WS── Browser B
                 (introduces peers)

Browser A <======== WebRTC DataChannel (P2P) ========> Browser B
           nonce -> token -> PIN -> file list -> chunks

No file data passes through the signaling server. It only relays connection setup messages (SDP offer/answer). All file transfer is peer-to-peer.

Tech stack

• Next.js 16 (static export -- no custom server needed for the UI)
• WebRTC with STUN (stun:stun.l.google.com:19302)
• Zustand for state management
• Tailwind CSS v4 with glassmorphism
• Web Crypto API for authentication handshake
• pako for SDP compression
• ws for the signaling server

Signaling server

server/signaling.ts -- a minimal WebSocket server (~100 lines):

• Clients connect and send a REGISTER message with device info
• Server assigns an ID, broadcasts peer join/leave events
• Relays OFFER/ANSWER messages between specific peers
• Ping/keepalive via empty messages

Configurable via PORT env var (default 8080).

Crypto handshake

On WebRTC DataChannel open, peers perform:

1. Nonce exchange (random 16 bytes each)
2. Token exchange (signed with Ed25519 or RSA-PSS, derived from nonce)
3. Optional PIN verification
4. File list transfer
5. Chunked file transfer (16KB chunks, 1MB backpressure threshold)

License

MIT