You don’t need to listen on same port if you follow convention

By convention when you request http://127.0.0.1 your browser will try to connect to port 80. If you try to open https://127.0.0.1 your browser will try to connect to port 443. So to secure all traffic it is simply conventional to listen to port 80 on http with a redirect to https where we already have a listener for https for port 443. Here’s the code:

var https = require('https');

var fs = require('fs');
var options = {
    key: fs.readFileSync('./key.pem'),
    cert: fs.readFileSync('./cert.pem')
};

https.createServer(options, function (req, res) {
    res.end('secure!');
}).listen(443);

// Redirect from http port 80 to https
var http = require('http');
http.createServer(function (req, res) {
    res.writeHead(301, { "Location": "https://" + req.headers['host'] + req.url });
    res.end();
}).listen(80);

Test with https:

$ curl https://127.0.0.1 -k
secure!

With http:

$ curl http://127.0.0.1 -i
HTTP/1.1 301 Moved Permanently
Location: https://127.0.0.1/
Date: Sun, 01 Jun 2014 06:15:16 GMT
Connection: keep-alive
Transfer-Encoding: chunked

If you must listen on same port

There isn’t simple way to have http / https listen on the same port. You best bet is to create proxy server on a simple net socket that pipes to (http or https) based on the nature of the incoming connection (http vs. https).

Here is the complete code (based on https://gist.github.com/bnoordhuis/4740141) that does exactly that. It listens on localhost:3000 and pipes it to http (which in turn redirects it to https) or if the incomming connection is in https it just passes it to https handler

var fs = require('fs');
var net = require('net');
var http = require('http');
var https = require('https');

var baseAddress = 3000;
var redirectAddress = 3001;
var httpsAddress = 3002;
var httpsOptions = {
    key: fs.readFileSync('./key.pem'),
    cert: fs.readFileSync('./cert.pem')
};

net.createServer(tcpConnection).listen(baseAddress);
http.createServer(httpConnection).listen(redirectAddress);
https.createServer(httpsOptions, httpsConnection).listen(httpsAddress);

function tcpConnection(conn) {
    conn.once('data', function (buf) {
        // A TLS handshake record starts with byte 22.
        var address = (buf[0] === 22) ? httpsAddress : redirectAddress;
        var proxy = net.createConnection(address, function () {
            proxy.write(buf);
            conn.pipe(proxy).pipe(conn);
        });
    });
}

function httpConnection(req, res) {
    var host = req.headers['host'];
    res.writeHead(301, { "Location": "https://" + host + req.url });
    res.end();
}

function httpsConnection(req, res) {
    res.writeHead(200, { 'Content-Length': '5' });
    res.end('HTTPS');
}

As a test, If you connect it with https you get the https handler:

$ curl https://127.0.0.1:3000 -k
HTTPS

if you connect it with http you get the redirect handler (which simply takes you to the https handler):

$ curl http://127.0.0.1:3000 -i
HTTP/1.1 301 Moved Permanently
Location: https://127.0.0.1:3000/
Date: Sat, 31 May 2014 16:36:56 GMT
Connection: keep-alive
Transfer-Encoding: chunked