Port 27017 (MongoDB)
Port 27017 is the default port of MongoDB (mongod and mongos). Applications and mongosh connect to the database here.
- Service
- MongoDB
- Protocol
- TCP
- IANA registry
- Officially assigned: mongodb (Mongo database system), TCP
Check if a port is open on your IP
We only check the address you are visiting from, one TCP port at a time. You cannot enter someone else’s address: this is not a port scanner.
Is it safe to open port 27017?
A MongoDB reachable on 27017 without authentication lets anyone read or delete its data. Follow MongoDB’s security checklist: enable access control, bind to private addresses, use TLS, and keep 27017 closed to the internet.
Sources
“Port 27017 is already in use”: how to fix it
The error means another program is already listening on port 27017. Find its process ID (PID), then stop that program or start yours on a different port.
Windows (Command Prompt or PowerShell as administrator)
netstat -ano | findstr :27017taskkill /PID <PID> /FmacOS
lsof -nP -iTCP:27017 -sTCP:LISTENkill <PID>Linux
sudo ss -ltnp | grep :27017sudo lsof -i :27017sudo kill <PID>Replace <PID> with the number from the last column (Windows) or the PID column (macOS, Linux).
Why a port can look closed when your server is running
Most home networks sit behind a router doing NAT: the router owns the public address, and your computer has a private one such as 192.168.1.10. A connection from the internet reaches the router and stops there unless you add a port forwarding rule to your computer.
Many mobile and some home providers go further and use carrier-grade NAT (CGNAT): several customers share one public address, and your router itself gets an address from 100.64.0.0/10. Then no rule on your side can open a port; ask the provider for a public IP or use a tunnel or VPN service.
Even with forwarding in place, the firewall on the computer (Windows Defender Firewall, ufw, firewalld) must allow the port, and the program must listen on all interfaces (0.0.0.0), not only on 127.0.0.1.
UDP cannot be checked this way: a UDP service usually stays silent to packets it does not understand, so “no answer” means nothing. This check uses TCP only.
Frequently asked questions
What is port 27017 used for?
Port 27017 is the default port of MongoDB (mongod and mongos). Applications and mongosh connect to the database here.
Is port 27017 TCP or UDP?
Port 27017 uses TCP. IANA registers it for TCP.
Is it safe to open port 27017?
A MongoDB reachable on 27017 without authentication lets anyone read or delete its data. Follow MongoDB’s security checklist: enable access control, bind to private addresses, use TLS, and keep 27017 closed to the internet.
How do I free port 27017 if it is already in use?
Find the process: on Windows run netstat -ano | findstr :27017 and stop it with taskkill /PID <pid> /F; on macOS or Linux run lsof -i :27017 and stop it with kill <pid>.