Add native SSL support

app.js

@@ -1,6 +1,8 @@
 'use strict';
 const config = require('./config');
 const app = require('./lib/endpoints');
+const https = require('https');
+const fs = require('fs');
 
 /**
  * Naming:
@@ -9,17 +11,43 @@ const app = require('./lib/endpoints');
  * fid: {sid}++{key}
  */
 
-const server = app.listen(config.port, config.iface, () => {
-  console.log(`PsiTransfer listening on http://${config.iface}:${config.port}`);
-});
+let server;
+if(config.port) {
+  // HTTP Server
+  server = app.listen(config.port, config.iface, () => {
+    console.log(`PsiTransfer listening on http://${config.iface}:${config.port}`);
+  });
+}
+
+let httpsServer;
+if(config.sslPort && config.sslKeyFile && config.sslCertFile) {
+  // HTTPS Server
+  const sslOpts = {
+    key: fs.readFileSync(config.sslKeyFile),
+    cert: fs.readFileSync(config.sslCertFile)
+  };
+  httpsServer = https.createServer(sslOpts, app)
+    .listen(config.sslPort, config.iface, () => {
+      console.log(`PsiTransfer listening on https://${config.iface}:${config.sslPort}`);
+    });
+}
 
 
 // graceful shutdown
 function shutdown() {
   console.log('PsiTransfer shutting down...');
-  server.close(() => {
-    process.exit(0);
-  });
+  if(server) {
+    server.close(() => {
+      server = false;
+      if(!server && !httpsServer) process.exit(0);
+    });
+  }
+  if(httpsServer) {
+    httpsServer.close(() => {
+      httpsServer = false;
+      if(!server && !httpsServer) process.exit(0);
+    });
+  }
   setTimeout(function() {
     console.log('Could not close connections in time, forcefully shutting down');
     process.exit(0);