Your server should use the HTTPS protocol to receive connections. You may do this by placing an HTTPS reverse proxy in front of your HTTP server, or by using https.createServer() instead of http.createServer().
If your app deals with or transmits sensitive data, use Transport Layer Security (TLS) to secure the connection and the data. This technology encrypts data before it is sent from the client to the server, thus preventing some common (and easy) hacks.