Weather update server in Node.js

// Weather update server in node.js
// Binds PUB socket to tcp://*:5556
// Publishes random weather updates

var zmq = require('zeromq')
, publisher = zmq.socket('pub');

publisher.bindSync("tcp://*:5556");
publisher.bindSync("ipc://weather.ipc");

function zeropad(num) {
return num.toString().padStart(5, "0");
};

function rand(upper, extra) {
var num = Math.abs(Math.round(Math.random() * upper));
return num + (extra || 0);
};

while (true) {
// Get values that will fool the boss
var zipcode = rand(100000)
, temperature = rand(215, -80)
, relhumidity = rand(50, 10)
, update = `${zeropad(zipcode)} ${temperature} ${relhumidity}`;
publisher.send(update);
}