node.js - Cannot open site with https server using Express -

var fs = require('fs'), https = require('https'), express = require('express'), app = express();  https.createserver({   key: fs.readfilesync('./ssl/key.pem'),   cert: fs.readfilesync('./ssl/cert.pem') }, app).listen(55555);  app.get('/', function (req, res) {   res.header('content-type', 'text/html');   return res.end('<h1>hello, secure world!</h1>'); }); 

i tried many times using https server based on express, while still cannot open site, example using chrome:

it says "no data received" , "err_empty_response".

so listening, response cannot sent client, why? thank you!