Whirtle

A Sendspin client for Windows.

Whirtle connects to Sendspin audio servers on your local network and plays back streamed audio with low-latency, clock-synchronized playback. It ships as both a full WinUI desktop app and a CLI harness.

Features

• Audio playback — Opus, FLAC, and PCM decoding via a jitter-buffered, clock-synchronized pipeline
• mDNS discovery — Advertises itself on the local network so Sendspin servers can find and connect to it automatically
• Now-playing metadata — Displays track title, artist, album, duration, and playback position
• Album artwork — Receives and displays binary artwork from the server
• Remote control — Accepts play, pause, skip, and volume commands from the server
• Audio device selection — Enumerates and selects Windows audio output devices
• System tray — Minimize to tray with quick restore
• Firewall integration — Prompts to add a Windows Firewall rule on first launch (required for server-initiated connections)
• Modern UI — Dark theme, Mica backdrop, WinUI 3

Requirements

• Windows 10 (build 17763) or Windows 11
• .NET 10 SDK (build only)
• x86, x64, or ARM64

The distributed application bundles the Windows App SDK runtime — no separate runtime install needed.

Building

git clone <repo-url>
cd whirtle/client
dotnet restore
dotnet build

Running the desktop app

cd src/Whirtle.Client.UI
dotnet run

Running the CLI harness

cd src/Whirtle.Client
dotnet run -- [--name <friendly-name>] [--port <port>]

Flag	Default
--name	Whirtle (<hostname>)
--port	8928

CLI commands (interactive prompt)

Command	Action
play	Resume playback
pause	Pause playback
skip	Skip to next track
volume <0–100>	Set volume
status	Show current metadata and artwork
quit / exit	Exit

Running tests

dotnet test

Project structure

client/
├── src/
│   ├── Whirtle.Client/        # Core library + CLI entry point
│   │   ├── Audio/             # Device enumeration
│   │   ├── Clock/             # NTP-style clock sync
│   │   ├── Codec/             # Opus, FLAC, PCM decoders
│   │   ├── Discovery/         # mDNS advertisement
│   │   ├── Playback/          # Jitter buffer + WASAPI renderer
│   │   ├── Protocol/          # Sendspin protocol client
│   │   ├── Transport/         # WebSocket transport
│   │   └── role.*/            # Metadata, controller, artwork, player roles
│   │
│   └── Whirtle.Client.UI/     # WinUI 3 desktop application
│       ├── Pages/             # NowPlaying, Settings, Logs
│       └── ViewModels/        # MVVM view models
│
└── tests/
    ├── Whirtle.Client.Tests/               # Unit tests (xUnit)
    └── Whirtle.Client.IntegrationTests/    # Integration tests

Protocol

Whirtle implements the Sendspin protocol spec and supports both connection modes:

• Client-initiated — Whirtle connects outbound to a known server
• Server-initiated — Whirtle advertises via mDNS (_sendspin._tcp.local.) and listens for incoming WebSocket connections on /sendspin (default port 8928)

License

GNU General Public License v3.0 — see LICENSE.