Port 27017 MONGODB
Port 27017 is the IANA-assigned mongodb port for Mongo database system (TCP).
What is port 27017 used for?
Port 27017 is assigned to mongodb and uses TCP. The IANA registry describes the service as “Mongo database system”. It sits above the registered range, where most numbers are transient client ports. A fixed high port is worth documenting precisely because tooling often assumes the default.
Ports are the transport-layer address a service listens on. A client that wants to reach mongodb connects to port 27017. If nothing is listening, the connection is refused. That is why a port conflict appears whenever two processes try to bind the same number.
Use the commands below to confirm whether port 27017 is actually in use before you change firewall rules. Blocking the port stops new inbound traffic at the firewall, but it does not stop a local process from listening, and it does not remove the service from the machine.
Source: IANA Service Name and Transport Protocol Port Number Registry. Registered assignee: [MongoDB_Inc.].
Check and block port 27017
Copy-ready commands for the protocols assigned to this port. Run the check first, then block only what should not be reachable.
Check on Linux
sudo ss -tlpn 'sport = :27017'Check on Windows
Get-NetTCPConnection -LocalPort 27017 -State Listen -ErrorAction SilentlyContinueBlock with UFW
sudo ufw deny 27017/tcpBlock with iptables
sudo iptables -A INPUT -p tcp --dport 27017 -j DROPThese commands are examples for a typical host. Check the listener before you change firewall rules, and persist iptables rules with iptables-save or netfilter-persistent. On Windows, use Windows Defender Firewall or New-NetFirewallRule for persistent blocks. The iptables rules here cover IPv4; mirror them with ip6tables if IPv6 is enabled.
Is port 27017 safe to expose?
MongoDB instances are frequently left without authentication and have suffered large-scale data theft. Enable auth, bind privately and use TLS. Treat this port as sensitive. Restrict it to trusted networks or a VPN, require authentication and logging, and never expose it directly to the public internet without a hardened gateway in front.
Where port 27017 is usually used
Most traffic on port 27017 falls into these scenarios. The demo below is a safe way to confirm the listener before you change anything.
- Application servers opening pooled connections to the database on port 27017.
- Migrations, backups and reporting jobs run from a trusted bastion host.
- Local Docker or test environments that publish the database on the host.
Open a MongoDB shell
Connect without a URI password; mongosh prompts for credentials when authentication is enabled.
mongosh "mongodb://127.0.0.1:27017"Common problems with port 27017
Connection refused or timed out
Refused usually means the host is reachable but nothing is listening on port 27017. A timeout more often means a firewall drop, a wrong host or a service bound to a different interface.
Port already in use
Find the process holding the port with sudo ss -tlpn 'sport = :27017' or sudo lsof -i :27017. Stop that process or configure it to bind another port; killing it without identifying it can take down a production service.
Firewall rule did not survive a reboot
UFW and Windows Firewall keep rules across restarts. Raw iptables rules do not: save them with iptables-save or the netfilter-persistent package, and re-apply after upgrades that reset the ruleset.
The port is blocked but still reachable
A firewall rule filters inbound traffic; it does not close the listener. Confirm with the check command above and bind the service to 127.0.0.1 when only local clients need it.
Port 27017 at a glance
| Port number | 27017 |
|---|---|
| Service name | mongodb |
| Transport protocol | TCP |
| Category | Databases |
| Range | High port (10001–65535) |
| Risk level | High |
| Registered assignee | [MongoDB_Inc.] |
| Registry description | Mongo database system |
| Source | IANA Service Name and Transport Protocol Port Number Registry |
Frequently asked questions
What is port 27017 used for?
Port 27017 (MONGODB) uses TCP. Mongo database system.
How do I check if port 27017 is open?
On Linux run `sudo ss -tlpn 'sport = :27017'`. On Windows run `Get-NetTCPConnection -LocalPort 27017 -State Listen -ErrorAction SilentlyContinue` in PowerShell. If the port is open, the output shows a process listening on port 27017; empty output usually means nothing is bound to it.
How do I block port 27017?
With UFW run `sudo ufw deny 27017/tcp`. With iptables run `sudo iptables -A INPUT -p tcp --dport 27017 -j DROP`. Persist the iptables rules with your distribution's netfilter-persistent or iptables-save tooling so they survive a reboot.
Is port 27017 safe to expose?
MongoDB instances are frequently left without authentication and have suffered large-scale data theft. Enable auth, bind privately and use TLS. Nevertheless, treat this port as sensitive. Restrict it to trusted networks or a VPN, require authentication and logging, and never expose it directly to the public internet without a hardened gateway in front.
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Primary data: IANA Service Name and Transport Protocol Port Number Registry.
Last reviewed 2026-10-30 · Methodology · About · Privacy