heroku port관련 error 수정

@@ -51,4 +51,8 @@ var app = http.createServer(function(request,response){
     response.end("Not found");
     }
 });
-app.listen(23000);
\ No newline at end of file
+app.listen(process.env.PORT || 23000, function(){
+
+    console.log("Express server listening on port %d in %s mode", this.address().port, app.settings.env);
+
+});
\ No newline at end of file