Port 9339 GNMI-GNOI
Port 9339 is the IANA-assigned gnmi-gnoi port for gRPC Network Mgmt/Operations Interface (TCP).
What is port 9339 used for?
Port 9339 is assigned to gnmi-gnoi and uses TCP. The IANA registry describes the service as “gRPC Network Mgmt/Operations Interface”. It sits in the registered range, the block used by databases, application servers and developer tooling. Port conflicts here are common when several local services start at once.
Ports are the transport-layer address a service listens on. A client that wants to reach gnmi-gnoi connects to port 9339. 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 9339 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.
Browse all RPC and service APIs ports
Source: IANA Service Name and Transport Protocol Port Number Registry. Registered assignee: [Google_Netops].
Check and block port 9339
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 = :9339'Check on Windows
Get-NetTCPConnection -LocalPort 9339 -State Listen -ErrorAction SilentlyContinueBlock with UFW
sudo ufw deny 9339/tcpBlock with iptables
sudo iptables -A INPUT -p tcp --dport 9339 -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 9339 safe to expose?
This port is not on our curated list of services with a widely exploited profile. Exposure is only safe when the listening service is intended, patched and protected by a firewall. Keep the listening service patched and remove it if unused. A default-deny firewall policy with explicit allow rules is still the safest baseline.
Where port 9339 is usually used
Most traffic on port 9339 falls into these scenarios. The demo below is a safe way to confirm the listener before you change anything.
- Service-to-service calls between application components.
- API gateways and clients that use a binary RPC protocol.
- Local development of microservices that expose a fixed RPC port.
Probe the RPC listener
RPC protocols need their own client; this only confirms the socket is reachable. For gRPC with reflection enabled, use grpcurl.
nc -vz 127.0.0.1 9339Common problems with port 9339
Connection refused or timed out
Refused usually means the host is reachable but nothing is listening on port 9339. 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 = :9339' or sudo lsof -i :9339. 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 9339 at a glance
| Port number | 9339 |
|---|---|
| Service name | gnmi-gnoi |
| Transport protocol | TCP |
| Category | RPC and service APIs |
| Range | Registered port (1024–10000) |
| Risk level | Standard/Low |
| Registered assignee | [Google_Netops] |
| Registry description | gRPC Network Mgmt/Operations Interface |
| Source | IANA Service Name and Transport Protocol Port Number Registry |
Frequently asked questions
What is port 9339 used for?
Port 9339 (GNMI-GNOI) uses TCP. gRPC Network Mgmt/Operations Interface.
How do I check if port 9339 is open?
On Linux run `sudo ss -tlpn 'sport = :9339'`. On Windows run `Get-NetTCPConnection -LocalPort 9339 -State Listen -ErrorAction SilentlyContinue` in PowerShell. If the port is open, the output shows a process listening on port 9339; empty output usually means nothing is bound to it.
How do I block port 9339?
With UFW run `sudo ufw deny 9339/tcp`. With iptables run `sudo iptables -A INPUT -p tcp --dport 9339 -j DROP`. Persist the iptables rules with your distribution's netfilter-persistent or iptables-save tooling so they survive a reboot.
Is port 9339 safe to expose?
This port is not on our curated list of services with a widely exploited profile. Exposure is only safe when the listening service is intended, patched and protected by a firewall. Nevertheless, keep the listening service patched and remove it if unused. A default-deny firewall policy with explicit allow rules is still the safest baseline.
Related ports
- Port 9306 · sphinxqlSphinx search server (MySQL listener)
- Port 9340 · gribigRPC Routing Information Base Interface
- Port 8710 · semi-grpcgRPC for SEMI Standards implementations
- Port 13832 · a-trust-rpcCertificate Management and Issuing
- Port 8117 · purityrpcPurity replication clustering and remote management
- Port 50051 · gRPCCommon default port for gRPC servers using HTTP/2
Primary data: IANA Service Name and Transport Protocol Port Number Registry.
Last reviewed 2026-10-30 · Methodology · About · Privacy