// http://stackoverflow.com/questions/10750303/how-can-i-get-the-local-ip-address-in-node-js
function getIPAddr() {
    var interfaces = os.networkInterfaces();
    for (var k in interfaces) {
        for (var k2 in interfaces[k]) {
            var address = interfaces[k][k2];
            if (address.family === 'IPv4' && !address.internal) {
                return address.address;
            }
        }
    }
    return null;
}