MongoDB

Localhost 27017 Error?

Port 27017 is the MongoDB standard. If connection is refused, your mongod process is likely down.

Fix MongoDB
Kill Port 27017
npx kill-port 27017

Fixing MongoDB Connection Refused

MERN stack developers often face this. It means your Node app cannot find the database on port 27017.

1. Check mongod status

Run the daemon command to see the live logs.

mongod

2. Delete Lock File (If crashed)

If Mongo crashed improperly, a lock file might prevent restart.

rm /data/db/mongod.lock

Developer Port Reference Guide

Frontend & Web
3000 React / Node / Default 3001 React Secondary 5173 Vite / Vue 3 4200 Angular CLI 8000 Django / Gatsby 8080 Tomcat / Vue / Spring 8081 React Native 80 HTTP Standard 443 HTTPS / SSL
Backend & Infrastructure
5000 Flask / AirPlay 4000 Jekyll / Hexo 9000 SonarQube / PHP
Database & Cache
3306 MySQL 5432 PostgreSQL 27017 MongoDB 6379 Redis 11211 Memcached
DevOps & Data Science
8888 Jupyter Notebook 9200 Elasticsearch 9090 Prometheus 15672 RabbitMQ UI 8500 Consul 127.0.0.1 Loopback IP