Friendly Audio Streaming Protocol (FASP)

A simple and open protocol for streaming audio in local networks.

Sort of like AirPlay and DLNA, but

• code & spec are openly available
• no DRM
• un-overengineered: XML JSON, reverse HTTP WebSockets
• flexible: any client can control playback & play new media

If you want to try it out, head over to Getting started.

How it works

A FASP receiver is a WebSocket server. Any number of clients can connect to it and send the following commands, encoded as JSON:

• ["play", "http://example.org/some-url"]
• ["queue", "http://example.org/some-url"]
• ["next"]
• ["previous"]
• ["remove", 2]
• ["stop"]
• ["resume"]
• ["pause"]
• ["seek", 123, false, false] (relative, in seconds)
• ["seek", 123, true, false] (absolute, in seconds)
• ["seek", 123, true, true] (absolute, in percent)
• ["seek", 123, false, true] (relative, in percent)
• ["set-volume", 70]
• ["get-props"]

The receiver may send the following commands to the client, encoded as JSON:

• ["prop", {"filename": …, "title": …, "album": …, "artist": …, "length": …, "progress": …, "volume": …, "playing": …}]
• ["prop", "filename", "some-file.ogg"]
• ["prop", "path", "path/to/some-file.ogg"]
• ["prop", "duration", 219.5]
• ["prop", "percent-pos", 2,477]
• ["prop", "time-pos", 54.5]
• ["prop", "pause", false]
• ["prop", "volume", 70]
• ["prop", "metadata", {title, album, artist, album_artist, track, disc}]
• ["prop", "artwork", "https://example.org/path/to/artwork.jpg"]
• ["prop", "queue", ["some-file.ogg", "another-file.mp3"]]

A receiver announces itself via mDNS, with the following properties:

• service type: _fasp._tcp.
• name: a url-safe, ASCII string
• id: a random hex ID, 16 characters
• version: the version of the protocol, 2 currently
• hostname
• port

Existing implementations

• fasp-server-cli – A proof-of-concept receiver based on mpv.
• fasp-client-cli – A proof-of-concept command line client.
• fasp-web-client – A proof-of-concept client web app.

Libraries

• fasp-client – A JS lib to connect to a receiver and send commands. It can also serve local files on demand, for the receiver to fetch. fasp-client-cli and fasp-web-client use it.
• search-fasp-receivers – Search for receivers in the local network.
• fasp-receiver – A JS lib to create & announce a receiver. You have to implement the audio playing.
• fasp-server – A JS lib to run a receiver, including audio playing. fasp-server-cli uses it.