# tether

Phone ↔ laptop clipboard relay. **v0.1 / MVP.**

Today this is an HTTP+SSE broadcast bus. The roadmap is what makes it
interesting: WebRTC for true P2P, Sign in with Apple for cross-device
identity, mDNS for same-LAN discovery, end-to-end encryption baked in.

```
phone (web UI)              tether-server                tether-client
─────────────               ─────────────                ──────────────
type/paste                  HTTP+SSE relay               Linux/Mac/Win
  │                              │                              │
  └─── POST /api/send ──────────▶│                              │
                                 ├──── event: clipboard ───────▶│
                                 │                              ▼
                                 │                          stdout / OS
                                 │                          clipboard
                                 │◀──── POST /api/send ─────────┘
                                 ▼
                          web UI shows it
```

## Quick start

```bash
go run ./server
# in another terminal
go run ./client -server http://localhost:8765

# send a one-shot message from CLI:
go run ./client -server http://localhost:8765 -send "hello"
```

Then open `http://localhost:8765/` on your phone (same network) and try
the buttons.

## Pieces

- `server/` — single Go binary. Embedded HTML page. Exposes:
  - `GET /` — phone UI
  - `POST /api/send` — accept a message
  - `GET /api/stream` — SSE feed of every published message
  - `GET /healthz`
- `client/` — CLI client. Subscribes to `/api/stream`, prints received
  messages to stdout. `-send` for one-shot send.
- `server/web/index.html` — phone UI (paste, send, live feed of incoming).

## Roadmap

| Phase | What | Why |
|---|---|---|
| **v0.1 (now)** | HTTP+SSE relay, single broadcast bus | Prove the shape end-to-end |
| v0.2 | mDNS service advertisement, QR pairing | Zero-config discovery |
| v0.3 | WebRTC data channel (Pion) — clients negotiate P2P after seeing each other via the server's signaling | True low-latency E2E (DTLS) |
| v0.4 | Sign in with Apple OAuth → stable `sub` ties multiple devices to one trust circle | Identity without account/password |
| v0.5 | OS clipboard hook on client (read + write) — phone copy → laptop paste appears automatically | The actual Universal-Clipboard UX |
| v0.6 | File drop (large blob over WebRTC), encrypted at-rest history | Snapdrop-like UX bundled in |
| v1.0 | macOS / Windows clients, push notifications when off-network, packaged installers | Product |

## Why E2E by default

WebRTC data channels mandate DTLS. Once we move from SSE relay (v0.1) to
P2P data channels (v0.3+), the server only ever sees encrypted bytes
(and only during signaling — not for the data itself). That's free
end-to-end encryption, modeled on Apple's Continuity but using
standardized protocols.

## Why Sign in with Apple

~80% of Windows users also own an iPhone. SiwA gives us a free,
privacy-respecting identity provider that returns a stable per-app
subject ID. Devices that authenticate to the same `sub` are in the same
trust circle automatically. No passwords, no per-app account.

## What this isn't

- Not a Snapdrop clone (no file drop yet)
- Not KDE Connect (no OS integration yet)
- Not Pushbullet (no server-side persistence)
- Not yet WebRTC (v0.1 is HTTP relay)

But the foundation is right.

## License

MIT