explicitly listen to all IPv4 interfaces

index.js

@@ -42,6 +42,10 @@ app.get("/api/:date?", (req, res) => {
 });
 
 // listen for requests :)
-var listener = app.listen(PORT, function () {
-  console.log("Your app is listening on port " + listener.address().port);
+var listener = app.listen(PORT, "0.0.0.0", function () {
+  console.log(
+    `Your app is listening on interface ${
+      listener.address().address
+    } and port ${listener.address().port}`
+  );
 });