let express = require('express');

let app = express();

app.use(express.static('public'));

app.listen(3000, () => {
  console.log("http://localhost:3000/");
});

@@ -97,20 +97,32 @@
 .listen(
-3000
+process.env.PORT
 , () =%3E 
@@ -159,12 +159,32 @@
 ost:
-3000
+%22 + process.env.PORT + %22
 /%22);

Change port to use env variable.