var sslcert = fs.readFileSync('mycert.pem');
var sslkey = fs.readFileSync('mykey.pem');
var sslca = fs.readFileSync('ca.pem');
var options = { cert: sslcert, key: sslkey, ca: sslca, ... other options ... };
options.agent = new https.Agent(options);
var req = https.request(options, function(res) {
  s = req.socket;
  if(!s.authorized) { my_callback('SSL API ERROR '+s.authorizationError); return; }
  // the remote end was OK
...