@grantler-instruments/mqtt-midi-bridge

Node daemon that bridges system MIDI (hardware or virtual ports) to MQTT MIDI topics using @grantler-instruments/mqtt-midi.

• Subscribes to {prefix}/in/... (commands from web UIs) → MIDI out
• Publishes {prefix}/out/... (events from your DAW/hardware) ← MIDI in

Requires Node 18+ and a working native build of @julusian/midi (RtMidi).

Install

Recommended — run with npx (no global install):

npx @grantler-instruments/mqtt-midi-bridge --help

Or install globally:

npm install -g @grantler-instruments/mqtt-midi-bridge
mqtt-midi-bridge --help

All examples below use mqtt-midi-bridge; with npx, prefix the command:

npx @grantler-instruments/mqtt-midi-bridge --url mqtt://localhost:1883 --prefix remote

Usage

Config file

Copy mqtt-midi-bridge.config.example.json and edit:

{
  "url": "mqtt://localhost:1883",
  "prefix": "remote"
}

On macOS and Linux, if you omit midiIn, midiOut, and virtual, the bridge creates a virtual port named mqtt-midi-bridge (same idea as Max, Protokol, etc.). Point your DAW at that port. Override with "virtual": "MyName" or --virtual.

Run:

npx @grantler-instruments/mqtt-midi-bridge --config ./mqtt-midi-bridge.config.json

CLI flags override the file. Optional mqttOptions is passed through to MQTT.js (username, password, clientId, etc.).

Windows: virtual ports are not auto-created. Use loopMIDI (or similar), then set midiIn / midiOut to those port names, or use --list-ports.

CLI only

List ports:

npx @grantler-instruments/mqtt-midi-bridge --list-ports

Minimal (macOS / Linux — auto virtual port):

npx @grantler-instruments/mqtt-midi-bridge \
  --url mqtt://localhost:1883 \
  --prefix remote

Your DAW sees mqtt-midi-bridge for MIDI in and out. Use the same prefix in your web app (MqttMidi({ prefix: "remote", ... })).

Custom virtual name or hardware / loopMIDI ports:

npx @grantler-instruments/mqtt-midi-bridge \
  --url mqtt://localhost:1883 --prefix remote --virtual my-midi-port

npx @grantler-instruments/mqtt-midi-bridge \
  --url mqtt://localhost:1883 --prefix remote \
  --midi-in "IAC Driver Bus 1" --midi-out "IAC Driver Bus 1"

Programmatic API

import { startBridge } from "@grantler-instruments/mqtt-midi-bridge";

const bridge = await startBridge({
  url: "mqtt://localhost:1883",
  prefix: "remote",
  midiIn: { mode: "name", name: "IAC Driver Bus 1" },
  midiOut: { mode: "name", name: "IAC Driver Bus 1" },
});

await bridge.stop();

License

MIT — see LICENSE.