open-access-control-api/serial.js

const SerialPort = require('serialport');
const Readline = require('@serialport/parser-readline');

var express = require('express'),
    app     = express(),
    http    = require('http'),
    server  = http.createServer(app),
    io      = require('socket.io').listen(server),
    scores  = {};

// listen for new web clients:
server.listen(8080);

// open the serial port. Change the name to the name of your port, just like in Processing and Arduino:
const port = new SerialPort("/dev/ttyUSB0", { baudRate: 9600 });

const parser = new Readline({ delimiter: '\r\n' });
port.pipe(parser)

// respond to web GET requests with the index.html page:
app.get('/', function (req, res) {
  res.sendFile(__dirname + '/index.html');
});

// listen for new serial data:
parser.on('data', line => console.log(`> ${line}`))

// listen for new socket.io connections:
io.on('connection', function (socket) {
    // get data from serial and send it to socket
    parser.on('data', line => {
        socket.emit('data', line)
    });
    // get data from socket and send it to serial
    socket.on('data', function (data) {
        console.log('data', socket.conn.remoteAddress, data)
        port.write(data+"\r") // we need to end each command with a CR
    });
    // send and log connect messages
    socket.volatile.emit('message', "hi "+socket.conn.remoteAddress);
    socket.on('message', function (data) {
        console.log('message',socket.conn.remoteAddress,data)
    });
});