Screener

Screener is a private, low-latency screen-sharing project for one game player and a small group of friends. Its accepted media target is WebRTC P2P-first, with a dedicated LiveKit SFU/UDP virtual parent feeding only the necessary roots when direct/STUN peer paths cannot serve them. Roots continue distributing to bounded peer descendants; this is not an always-SFU conferencing design. Viewers should be able to join from a desktop or mobile browser without installing the sender application.

The first measurable Web proof of concept is implemented. A host captures a screen, window, or browser tab and shares a random four-digit room code plus an independent fragment invitation. During a share, the host can change between three ceiling profiles without reopening the source picker, pause, and switch sources. Browser video is fixed VP8 and leaves the video content hint unset. Code-only entry defaults to open after site access and may instead require a room password or be disabled; a valid grant enters directly. Rooms are process-memory state with a configurable dormant lease and disappear on restart. Lightweight deployments may keep independent direct WebRTC connections. The flagship deployment enables the all-room controller with bounded peer descendants and one LiveKit Host publication serving admitted Viewer subscriptions. Production admits 20 viewers; that admission limit is not a performance promise.

This is not yet a broadly validated product release; Current status owns the deployed revision and validation evidence. The deployed flagship boundary is the all-room bounded peer/SFU-UDP controller plus the memory-resident room/access model on screener-v11, with ordinary peer ICE kept STUN-only and no TURN or TCP media route. The optional Windows native sender remains source-only and is not a production runtime. Mobile devices are Web viewers only; ordinary Android and iOS browsers do not expose reliable screen capture for a Web Host. Real cross-network SFU media, game audio, a sustained public-network 1:20 session, mobile browser lifecycle behavior, and latency targets still require the documented manual test matrix.

Run locally

Node.js 24 and npm 11 are required.

npm ci
npm run dev

Production requires an independent 8-128 byte visible-ASCII SITE_ACCESS_PASSWORD. It protects room creation, Host role, and code-only Viewer entry. A valid room-scoped fragment grant enters directly without it; otherwise code-only entry needs site access before the room's open | password | disabled policy is evaluated. Local development and tests may leave it empty.

Open http://localhost:8787. The server listens on 0.0.0.0 by default so a phone on the same LAN can load http://<computer-lan-ip>:8787. To generate an invite that the phone can open while the host keeps using secure-context localhost capture, set PUBLIC_BASE_URL to that LAN URL and include both origins in ALLOWED_ORIGINS. LAN viewers can join over HTTP; the sharing page must remain on localhost or HTTPS because screen capture requires a secure context. The local default has no STUN, so cross-network use still requires HTTPS and the production ICE configuration documented separately.

SITE_ACCESS_PASSWORD supplies site access; valid room fragment grants bypass that gate only for the exact Viewer role, while code-only entry requires site access before code policy is evaluated. Ordinary ICE contains only self-hosted STUN. LiveKit supplies bounded SFU/UDP subscriptions when direct/peer paths cannot serve an edge; Screener configures no TURN or TCP media route. HTTPS/WSS remains TLS/TCP independently.

Run the complete automated validation with:

npm run check

Start here:

• Requirements
• WebRTC PoC design
• Deployment and media transport
• Feasibility research
• Current project memory
• Current status
• Architecture decision
• Contributing and Git workflow
• Documentation index