server.js

var express = require('express');
var app = express();
var http = require('http').Server(app);
var io = require('socket.io')(http);

app.use(express.static(`${__dirname}/public`));

var tessel = require('tessel');
var accel = require('accel-mma84').use(tessel.port['A']);
var av = require('tessel-av');
var camera = new av.Camera();

app.get('/stream', (request, response) => {
    response.redirect(camera.url);
});

// var calib = [0, 0]; // calibration shift

console.log('Accelerometer is initializing...');
accel.on('ready', function() {
    // Stream accelerometer data
    console.log('Accelerometer is ready...');
    io.on('connection', function(socket) {
        console.log('A user is connected...');
        // Initialize the accelerometer.

        var blinkID;

        function ledBlink() {
            blinkID = setInterval(blink, 100);
        }

        function blink() {
            tessel.led[2].toggle();
            // console.log('blink!');
        }

        accel.on('data', function(xyz) {
            socket.emit('newdata', {
                x: xyz[0],
                y: xyz[1],
                z: xyz[2],
            });
            // console.log('x:', xyz[0] - calib[0], 'y:', xyz[1] - calib[1], 'z:', xyz[2]);
        });

        accel.on('error', function(err) {
            // console.log('Error:', err);
        });

        // socket.on('newcalib', function(newcalib) {
        //     calib[0] = newcalib[0];
        //     calib[1] = newcalib[1];
        //     // console.log('New calibration => x: ' + calib[0] + ', y: ' + calib[1]);
        // });

        socket.on('ledon', function() {
            tessel.led[3].on();
            // console.log('Led is on.');
        });

        socket.on('ledoff', function() {
            tessel.led[3].off();
            // console.log('Led is off.');
        });

        socket.on('greenon', function() {
            clearInterval(blinkID);
            tessel.led[2].on();
            // console.log('Green light is on.');
        });

        socket.on('greenoff', function() {
            clearInterval(blinkID);
            tessel.led[2].off();
            // console.log('Green light is off.');
        });

        socket.on('greenblink', function() {
            clearInterval(blinkID);
            ledBlink();
            // console.log('Green light is blinking.');
        });
    });
});

http.listen(3000, function() {
    console.log('listening on *:3000');
});