Problems by setting up a encrypted Nodejs WebSocket-Server

I'm trying to get a nodejs wss-server up and running. For this I'm using the Express4 Framework and the eniaros/ws module.

But sadly I'm not able to get the WSS-Server up and running. The normal WS-Server is working quite fine, but every time I try to connect to my WSS the client gets connected and directly disconnected again.

My certs are self-signed.

My code is shown below. It would be awesome if some one could please help me!

var express = require('express');
var router = express.Router();
var app = express();

var http = require('http');
var https = require('https');
var WebSocket = require('ws').Server;
var path = require('path');
var fs = require('fs');

// Routes
app.use('/', require('./routes/index'));    

// Load config files
var db_conf = require('./config/vops_db_config.json');
var server_conf = require('./config/vops_server_config.json');

// TLS-Files
var cert_basepath = './config/certs/';
var tls_key = fs.readFileSync(cert_basepath + server_conf.tls.key_path);
var tls_cert = fs.readFileSync(cert_basepath + server_conf.tls.cert_path);
var https_options = {
    ssl: true,
    port: 3030,
    key : tls_key,
    cert: tls_cert
};

// Start all HTTP-Servers
var httpServer  = http.createServer(app);
var httpsServer = https.createServer(https_options, app);

httpServer.listen(3000, function () {
    console.log('HTTP-Server now listening on port ' + 3000);
});

httpsServer.listen(3030, function(){
    console.log('HTTPS-Server now listening on port '+ 3030);
});       

// Start WebSocket-Server
var wss = new WebSocket( { server: httpServer });

wss.on('connection', function(ws) {
    ws.on('message', function(message) {
        console.log('received: %s', message);
    });
    ws.send('something');
});