title: ERR_SSL_PROTOCOL_ERROR - Socket.io and Node.js
body: <p>I’m working with the Node.js server and using the Socket.io to manage connections by Socket but I’m having a problem with the SSL certificate.
  Lot of users can access the Node.js server normally, but others users doesn’t access and they receive this error:
  <a href="https://i.stack.imgur.com/Z5AVd.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/Z5AVd.png" alt="User error"></a></p>
  
  <p>When I set my server I have this SSL options:</p>
  
  <pre><code>var privateKey = fs.readFileSync('/root/cert/key.key', 'utf8').toString();
  var certificate = fs.readFileSync('/root/cert/cert.crt', 'utf8').toString();
  var ca = fs.readFileSync('/root/cert/ca.crt').toString();
  var credentials = { key: privateKey, cert: certificate, ca: ca };
  var app = express();
  var httpsServer = https.createServer(credentials, app);
  var io = require('socket.io')(httpsServer);
  </code></pre>
  
  <p>Somebody knows how to resolve this error? The problem is only some users receive this error.</p>