Did you mean to connect to localhost:27017?

Did you mean to connect to: mongodb://localhost:27017?

Port 27017 is for MongoDB database connections. Use mongo shell or your application driver to connect.

💡 Pro Tip: Port 27017 is MongoDB's default port. If you're getting connection errors, check if MongoDB service (mongod) is running.

Quick Commands for MongoDB Port 27017

Check if MongoDB is running:
sudo systemctl status mongod (Linux)
brew services list | grep mongodb (Mac)
tasklist | findstr mongod (Windows)
Connect to MongoDB:
mongo (Legacy shell)
mongosh (New shell)
mongo mongodb://localhost:27017/database
Find what's using port 27017:
lsof -i :27017 (Mac/Linux)
netstat -ano | findstr :27017 (Windows)
Start MongoDB service:
sudo systemctl start mongod (Linux)
brew services start mongodb-community (Mac)
net start MongoDB (Windows)

About Port 27017

Port 27017 is the default port for:

Common MongoDB Connection Issues

"Error: couldn't connect to server localhost:27017"

MongoDB server is not running or not accessible:

Solutions:

  • Start MongoDB: sudo systemctl start mongod
  • Check if MongoDB is installed: mongod --version
  • Verify MongoDB is listening: netstat -tlnp | grep 27017
  • Check MongoDB logs: sudo tail -f /var/log/mongodb/mongod.log
  • Try starting manually: mongod --dbpath /data/db

"MongoServerError: Authentication failed"

Authentication error when connecting to MongoDB:

Solutions:

  • Connect without auth: mongo --authenticationDatabase admin
  • Create admin user: 
    use admin
db.createUser({
  user: "admin",
  pwd: "password",
  roles: [ { role: "userAdminAnyDatabase", db: "admin" } ]
})
  • Connect with credentials: mongo -u admin -p password --authenticationDatabase admin
  • Check if auth is enabled in mongod.conf

"Error: ENOENT: no such file or directory, open '/data/db'"

MongoDB data directory doesn't exist:

Solutions:

  • Create data directory: sudo mkdir -p /data/db
  • Set permissions: sudo chown -R mongodb:mongodb /data/db
  • Specify custom path: mongod --dbpath /custom/path
  • Check mongod.conf for dbPath setting

"Port 27017 is already in use"

Another process is using MongoDB's port:

Solutions:

  • Find the process: lsof -i :27017
  • Stop existing MongoDB: sudo systemctl stop mongod
  • Kill process: sudo kill -9 PID
  • Change MongoDB port in mongod.conf: 
    net:
  port: 27018
  • Restart MongoDB: sudo systemctl restart mongod

"MongoNetworkError: failed to connect to server"

Network connectivity issues with MongoDB:

Solutions:

  • Check firewall settings
  • Verify bindIp in mongod.conf: bindIp: 127.0.0.1
  • Test connection: telnet localhost 27017
  • Check if MongoDB is bound to all interfaces: bindIp: 0.0.0.0
  • Verify DNS resolution: ping localhost

Related Database Ports

Useful MongoDB Resources