Composer Reference Guide R2-2026-2.6.9642.28010

Web API

The Web API tab gathers everything network-facing on Composer — the HTTP REST API surface (used by Connectors, dashboards, and external automation), the WebSocket push channel (used for real-time event subscriptions), and the UDP discovery service that lets multiple Composer hosts find each other on the local network.

Settings window — Web API tab

Activate the Web API to enable external application control using HTTP or Web Sockets.

For the full endpoint catalogue see the HTTP API manual; for the message envelope and subscription channels of the push channel see the WebSockets manual.

API-key authentication is configured separately, not on this tab. Composer reads valid keys from apikeys.json next to the executable; see HTTP API → Authentication for the file format and behaviour when no keys are defined.

HTTP API

  • Enable Web API (EnableHttpApi) — master switch for the HTTP API. When off, the listener doesn't bind to its port and every endpoint is unreachable. Default: on.
  • Web API listening port (HttpApiPort) — TCP port the HTTP API listens on. Clamped to 1–65536. Default: 44433. Changing the port requires a Composer restart.
  • Web API Https FQDN (HttpsFQDN) — fully qualified domain name used to bind an HTTPS certificate (via the Windows HTTP Server API certificate store) to the listener. Empty disables HTTPS — Composer serves HTTP only. Changing the FQDN requires a Composer restart.
  • Disable Web Api when project not running (DisableWebApiWhenNotRunning) — when on, the HTTP API rejects every request while the engine is not in Running state, except a small whitelist (/api/start, /api/stop, /api/quit, /api/exit, /api/discovery/*). Useful on production hosts where you don't want third-party callers poking at a stopped Composer. Default: on.

Connectors

Connectors are project-defined HTTP triggers — the project-level surface that lets external systems invoke a saved sequence of API commands (set property, execute command, etc.) by name. This single setting decides what happens when a Connector fires while another one is still running.

  • Connector behaviour (ConnectorRestrictions) — concurrency policy:

    • Default (always allow connectors to be invoked) — the new Connector runs side-by-side with whatever's already in flight. Use when each Connector targets distinct components and races aren't a concern.
    • Warn — the new Connector runs, but a warning is logged so you can spot the overlap in monitoring.
    • Warn and Prohibit — the new Connector is rejected with a warning if another is active. Use when Connectors set conflicting properties.
    • Stop Running Connectors — any in-flight Connector is cancelled and the new one runs.

    Runtime-mutable via /api/settings/set so a script or remote operator can swap policies without a restart. Default: Default (always allow).

WebSockets

The WebSocket server pushes real-time events (property changes, audio levels, system info, log lines) to subscribed clients and accepts a small set of command messages. Off by default — turn it on only when a client (a custom dashboard, a remote control surface) needs the push channel.

  • Enable WebSockets (EnableWebSockets) — master switch. Restart Composer for the change to take effect — the listener is started during application startup. Default: off.

  • Hostname (WebSocketsHostName) — interface the listener binds to. localhost for local-only access; an IP or hostname to expose on a private network. Default: localhost.

  • Port (WebSocketsPort) — TCP port the listener uses. Default: 8081.

  • Throttled properties update frequency (WebSocketThrottledPropertiesFrequency) — cadence at which property-change pushes (audio mixer, render status) are emitted, expressed as a frame divisor:

    • Default (Composer decides) — engine picks the cadence based on subscriber count.
    • Every frame, every 2nd, 3rd, 4th, 5th, 10th, 20th, 30th frame — fixed cadence.

    Lower frequency = smaller per-second message volume, smoother on slow links and many-subscriber setups. Default: Default.

  • Max incoming message queue length (1–500) (WebSocketsMaxIncomingMessageQueueLength) — per-connection backlog of inbound messages. The listener drops new messages from a client once its queue is full, so a client that stops draining can't pile up unbounded server memory. Default: 20.

  • Max outgoing message queue length (2–50000) (WebSocketsMaxOutgoingMessageQueueLength) — per-connection backlog of outbound messages. When the queue fills, the listener clears it (and disconnects the client) rather than blocking the engine. Default: 5000.

  • Max number of audio mixer subscribers (0–10) (WebSocketsMaxConnectedSubscribers) — caps how many WebSocket clients may subscribe to the high-volume AudioMixer channel simultaneously. Audio-meter pushes are bandwidth-heavy; allowing too many subscribers can saturate a small uplink. Default: 1.

Discovery Service

The Discovery Service announces this Composer's presence on the local network via UDP broadcast and listens for peers. Useful when building a control panel that needs to enumerate Composer hosts on the LAN without hard-coding addresses, or when a script wants to talk to a sibling Composer via /api/discovery/instances.

  • Enable Discovery Service (EnableDiscoveryService) — master switch. Default: off.
  • Discovery port (DiscoveryPort) — UDP port used for the broadcast / listen. All Composer instances must use the same port to discover each other. Clamped to 1–65535. Default: 5354.

The WebSocket server also exposes two audio-precision knobs — WebSocketMsgAudioDecimals and WebSocketMsgAudioRmsDecimals — but those live under Audio → Monitoring precision since they affect audio-meter readings rather than the listener itself.