Realm-js and Node.js: exception during login to Realm Object Server

I'm continue my tests of the realm-js. I wrote little test to check synchronization with server:

'use strict';

var Realm = require('realm');

const SmsSchema = {
    phone: 'string',
    msg: 'string',
    uuid: 'string',
    status: 'int'
};

var realm;
Realm.Sync.User.login('http://xx.xxx.xxx.xx:9080','login','password', (error, user) => {
    if (!error) {
        realm = new Realm({
            sync: {
                user: user,
                url: 'realm://xx.xxx.xxx.xx:9080/~/SMSService',
            },
            schema: [SmsSchema]
        });
    }
    else
        console.log('Connection error!');
});


realm.close();

After start of this test I have got the following exception:

Realm.Sync.User.login('http://xx.xxx.xxx.xx:9080','login','password', (error, user) => {
      ^

TypeError: Cannot read property 'User' of undefined
at Object.<anonymous> (/home/hermann/WebstormProjects/SMSService/app.js:15:11)
at Module._compile (module.js:570:32)
at Object.Module._extensions..js (module.js:579:10)
at Module.load (module.js:487:32)
at tryModuleLoad (module.js:446:12)
at Function.Module._load (module.js:438:3)
at Module.runMain (module.js:604:10)
at run (bootstrap_node.js:394:7)
at startup (bootstrap_node.js:149:9)
at bootstrap_node.js:509:3

Can anybody help me with this error? I have to add that I never before met Node.js and and my last experience with JavaScript was more than one year ago...

via Hermann