Tutorial. How to create MIDI synthesizer with MIDI API and Node JS https://medium.com/nebo-15/tutorial-how-to-create-midi-synthesizer-with-midi-api-and-node-js-48d41c162009

midi-api_step3_client.js

// WEBSOCKETS
var socketUrl = 'ws://' + location.hostname + ':3001';
var client = new BinaryClient(socketUrl);
var MIDIStream = null;
client.on('open', function () {
  MIDIStream = client.createStream();
  MIDIStream.on('data', handleReceiveAudioData);
  MIDIStream.on('end', handleEndAudioStream);
});
function handleReceiveAudioData(data) {
  console.log('receive audio data', data);
}
function handleEndAudioStream(data) {
  console.log('end', data);
}