Google Cast Vertical Architecture

The Google Cast vertical integrates homectl with Chromecasts, Google TV Streamers, and Google Nest Hub displays across the local network.

Architectural Diagram

Receiver Routing: Discovers active display receivers and routes media playback to the appropriate device based on user room context.
Volume Normalization: Maps human-readable volume percentages (0–100%) to the Cast SDK’s internal floating-point scale (0.0–1.0).
Display Status & App Tracking: Inspects active receiver channels to determine if a screen is actively streaming or resting on the backdrop screen.

cast_list_devices (🔒 Read-Only): Lists all discovered Cast devices with friendly names, models, and clean IPv4 addresses.
cast_get_status (🔒 Read-Only): Queries active receiver application (app_id, display_name), current volume, mute status, and status text.
cast_control (⚡ Mutating): Issues media transport actions (play, pause, stop, volume, mute, unmute).

go-chromecast Encapsulation: Uses application.NewApplication(application.WithCacheDisabled(true)) to guarantee internal cache initialization and eliminate nil-pointer panics.
IPv4 Prioritization: mDNS discovery for _googlecast._tcp inspects TXT records (fn, md, id) and explicitly prioritizes AddrIPv4 addresses, discarding unroutable or link-local IPv6 addresses (fd7a:...) so web clients and APIs connect reliably.
Resource Cleanup: Enforces defer app.Close(false) on all socket connections to prevent orphaned TLS channels on target devices.

Port 8009 TLS: Communication uses protocol buffer (protobuf) frames transmitted over an authenticated TLS socket on port 8009.
Hardware: Works across Chromecast with Google TV, Nest Hub Max, Google Home Mini, and third-party TVs with built-in Chromecast support.