node-red-contrib-play

Output node for Node-RED that triggers local audio playback via a command-line player.

What it does

The playa node receives a message, asks the underlying play-sound helper to start playback for a file path, then forwards the same message to its output (by default right after playback starts). Optionally you can send the message after the player exits, and you can stop the previous playback when a new message arrives. Playback errors are reported on the node (via node.error).

Requirements

• Node-RED >= 2.0.0
• Node.js >= 18
• A supported audio CLI on the machine running Node-RED (see play-sound). Typical choices:
  • macOS: afplay (often preinstalled)
  • Linux: aplay, mpg123, mplayer, or SoX play (package names vary by distribution)
  • Windows: e.g. cmdmp3 or another player you install and expose on PATH

Palette labels, dialog text, and the Info sidebar help for playa are translated for multiple editor locales (see locales/ in this package). The language follows the Node-RED editor language setting.

Install

From the directory where Node-RED is installed (or your user data directory, depending on your setup):

npm install node-red-contrib-play

Restart Node-RED, then find playa under the output category in the palette.

Linux (Debian/Ubuntu)

SoX is a common way to get the play command and broad format support:

sudo apt-get install sox libsox-fmt-all

Listing available players on the host (CLI)

The editor dropdown uses the same discovery as this package’s helper script: it runs which / where for each known CLI name. It does not decode audio files; it only checks that the binary exists on PATH for the Node-RED process.

From a clone of this repo (or after npm install in the package folder):

pnpm run players:list
# or: node scripts/print-available-players.mjs
# JSON: node scripts/print-available-players.mjs --json

macOS: to confirm afplay can open a real file (exit code 0), from the repo:

pnpm run players:verify-afplay

If that fails, the problem is outside Node-RED (path, permissions, or afplay itself).

Usage

Message contract

| Property | Role | |---------------|--------------------------------------------------------------------------------------------------------------------------------------| | msg.payload | Path to the sound file (string). If missing or empty, the node uses Sound file path from the node, then Name, as the path. | | Output timing | Controlled by Send output when playback finishes: off = send after playback starts (default); on = send after the player exits successfully. | | Overlap | Stop previous playback (default on) ends the last player process before starting the next file; turn off to allow overlapping sounds. |

By default the node sends the incoming message to the output right after playback starts (same object reference). If Send output when playback finishes is enabled, the message is sent after the player process exits successfully instead. Connect downstream nodes if you need to chain logic after a play request or after playback ends.

Editor fields

• Name: Node label in the editor and the last fallback path when msg.payload and Sound file path are empty.
• Sound file path: Optional absolute path on the Node-RED host. Use Choose file & upload to pick a file; the dialog shows uploading, then success with the saved path or an error message next to the button. Files are stored under node-red-contrib-play/uploads inside your Node-RED user directory (generated filename). Allowed extensions: .wav, .mp3, .ogg, .flac, .m4a, .aac; maximum size 10 MB per upload. Exported flows do not include uploaded binaries—copy or back up that folder if you move instances.
• Preview: The dialog includes a small browser Preview player that streams the file through the Node-RED admin HTTP API only when the resolved path stays inside your Node-RED user directory (same extensions as uploads); paths elsewhere on the host cannot be previewed in the editor.
• Player: The dropdown is filled from the Node-RED server (not the browser): it lists CLI players that match the server OS and, when possible, that are found on PATH. Choose Automatic to let play-sound pick the first available binary in that order. A value saved from another machine/OS may still appear as an extra option so the flow stays editable.
• Stop previous playback: When enabled (default), starting a new sound stops the still-running player from the previous input. Disable to allow overlapping playback from rapid triggers.
• Editor stop button: Like Inject/Debug, playa has a small button on the node edge in the editor. It POSTs to the admin HTTP API (/contrib-playa/stop/:id) to stop playback for that node on the runtime host. Deploy the flow first; requires the same flows.write permission as changing flows. If nothing is playing, the call still succeeds.
• Send output when playback finishes: When enabled, msg is sent after the player exits successfully; when disabled (default), msg is sent immediately after the play process is spawned (legacy behaviour).
• Status: While a local file is playing, the node badge can show approximate remaining time (e.g. ~1:23), derived from file metadata. HTTP(S) URLs or formats where duration cannot be read keep the plain blue playing indicator. The estimate may drift slightly from the CLI player’s actual progress.

Example flow

1. Add an inject node and set payload to an absolute path to a .wav or .mp3 on the host (for example /path/to/your/sound.wav on Linux/macOS).
2. Wire inject → playa → (optional) further nodes.
3. Deploy and click the inject button.

Ready-made flows are in the package (see examples/README.md):

• examples/Play sound from payload.json — set payload to an audio file path.
• examples/Play bundled beep.wav.json / Play bundled beep.mp3.json — bundled samples examples/sounds/beep.wav and beep.mp3 (when the default install layout matches).
• examples/Play bundled beep compare wav and mp3.json — try WAV and MP3 side by side.

Import via Menu → Import in the Node-RED editor.

Minimal flow (excerpt):

[
  {
    "type": "inject",
    "name": "play file",
    "payload": "/path/to/your/sound.wav",
    "payloadType": "str",
    "wires": [["playa-node-id"]]
  },
  {
    "type": "playa",
    "name": "",
    "player": "afplay",
    "wires": [[]]
  }
]

Replace the payload with a real file path on the machine where Node-RED runs.

Troubleshooting

• No sound: Confirm the file exists, the path is correct for the OS user running Node-RED, and a player binary is installed and on PATH.
• spawn … ENOENT: The chosen CLI (for example mplayer) is not installed or not on PATH for the Node-RED process. Install it, use Automatic so only players that resolve on this host are used, or pick another Player. If you saved a flow from another machine, an invalid player name is ignored with a warning and automatic selection is used.
• Player "…" exited with code 1: afplay (or another CLI) started but rejected the file—often wrong/missing path, unsupported format, or permissions. The node now checks that a local file exists before spawning the player. If you still see exit code 1, the file exists but the player cannot decode it—try WAV, another Player, or run pnpm run players:verify-afplay on macOS to test afplay outside Node-RED.
• Upload fails in the editor (403 / CSRF): Ensure your Node-RED version supplies a CSRF token to the editor; the upload request sends X-CSRF-Token when available. If uploads always fail, check the browser network tab for the /contrib-playa/upload response body.
• Errors in the debug sidebar: Read the message from node.error; it usually reflects the underlying player or spawn failure.

Contributing

See CONTRIBUTING.md for how to run tests and load this package into a local Node-RED while developing.

Thanks

1. This node builds on ideas from say / console audio patterns — thanks to Marak and the ecosystem.
2. Node-RED is a core tool for wiring IoT and automation flows; it is open source and was created at IBM.