appletree.js

var net = require('net');
var EventEmitter = require('events').EventEmitter;

// just define this in the file scope, you don't need to assign it as a property
var numApples = 50;

// pickers, because this can handle multiple pickers
var fruitPickers = new EventEmitter();

// replentish apples every thirty seconds
setInterval(function() {
	numApples++;
}, 30000);

// you don't instantiate the net module, you just call createServer
var server = net.createServer(function(fruitPicker) {
	// this is more common, there's really no point in setting this as a property
	var pickedApples = 0;

	// the server doesn't emit data events, just the individual connection
	fruitPickers.on('pickOne', function() {
		fruitPicker.write('A fruitBat picked an apple. ' + numApples + ' left.');
	})

	fruitPicker.setEncoding('utf-8');
	fruitPicker.on('data', function(data) {
		// always use triple-equals, it doesn't do weird and inefficient type conversions (0 === 0, but 0 !== '0')
		if (data[0] === 'p') {
			pickedApples++;
			numApples--;
			fruitPickers.emit('pickOne');
		}
	});
});

var port = 3000 || process.env.PORT;
server.listen(port, function() {
	console.log('listening on', port);
});