Blockcast Beacon runs a local multicast bridge on your Android device for the web pages you allow. A page requests streams through the window.multicast API. Beacon joins those multicast groups on your local network, or reaches them through an AMT relay (RFC 7450) over a unicast path, and forwards the packets to the page over WebTransport (QUIC). Playback, decoding and controls stay in your browser: Beacon has no player of its own.

How it works
1. Tap Start runtime. The bridge runs as a foreground service with an ongoing notification, so it keeps running while you use your browser. Stop it in the app or from the notification.
2. Open a page that uses window.multicast in a browser with WebTransport support, such as Chrome. Or tap Open in browser: it loads https://blockcast.network/live in your default browser with this bridge's address and certificate fingerprint attached, and that page can use Beacon for its AMT and native multicast choices.
3. The page chooses its streams, transport and relay. Beacon handles source-specific and any-source joins and AMT tunnels, then forwards each subscription to the page.

Site access
• The bridge checks every request's origin against your Allowed sites list, matched exactly. Edit the list in the app.
• For unknown sites, choose Ask to add, Deny, or Allow and add. With Ask, Beacon posts a notification and you allow or deny the site in the app.
• Browsers on this device connect over loopback and check the bridge's SHA-256 certificate fingerprint.
• Sites recognize the bridge by its device identity. Revoke enrollment and every site treats the next start as a new bridge.

Local network
Beacon also listens on the device's private LAN address (RFC 1918 or IPv6 ULA) and advertises the bridge over DNS-SD (_multicast-bridge._udp), so Blockcast clients on other devices can find it. If you deny local network access, other devices cannot reach the bridge, but browsers on this device still connect.

Live counters
Each connected browser shows its origin, connection time, and whether it is on this device or the LAN. Each subscription shows group, port, source and transport (native multicast or AMT), receive and forward rates, packet and byte counts, filtered and page-queue drops, and AMT member-queue overrun and peak.

What you need
• A page or service that uses window.multicast and names its streams and AMT relay. Beacon brings no content, account or relay of its own.
• For native multicast, a network that delivers the groups to this device.

Developers: the window.multicast API is open source (MIT) at https://github.com/Blockcast/beacon, published as the @blockcast/multicast-browser package.

Support: support@blockcast.net