Port 4318: OpenTelemetry (OTLP HTTP)

What uses port 4318

OTLP over HTTP posts protobuf or JSON to paths like /v1/traces on port 4318. It works in browsers and through proxies that don’t support gRPC, which makes it the default for many SDKs, including the JavaScript one.

Should port 4318 be open to the internet?

Keep private. Never expose this port to the internet. Keep it on localhost, a private network or behind a VPN or SSH tunnel.

Check what is listening on port 4318

sudo ss -ltnp 'sport = :4318'

sudo lsof -nP -iTCP:4318 -sTCP:LISTEN

Get-NetTCPConnection -LocalPort 4318 -State Listen
netstat -ano | findstr :4318

No output means nothing is listening. If a service should be, check that it is running and which address it binds to: 127.0.0.1 only accepts local connections, 0.0.0.0 or :: accepts them on every interface.

Fix “address already in use” on port 4318

Another process already holds the port. Find it with the commands above, then stop that service properly, or end the process:

sudo kill $(sudo lsof -t -iTCP:4318 -sTCP:LISTEN)

Stop-Process -Id (Get-NetTCPConnection -LocalPort 4318 -State Listen).OwningProcess

Allow port 4318 from trusted networks only

The examples allow 4318 only from 10.0.0.0/8; replace it with your own private network, office IP or VPN range.

sudo ufw allow from 10.0.0.0/8 to any port 4318 proto tcp
# Close it again:
sudo ufw delete allow from 10.0.0.0/8 to any port 4318 proto tcp

sudo firewall-cmd --permanent --add-rich-rule='rule family="ipv4" source address="10.0.0.0/8" port port="4318" protocol="tcp" accept'
sudo firewall-cmd --reload

New-NetFirewallRule -DisplayName "OpenTelemetry (OTLP HTTP) 4318/TCP" -Direction Inbound -Protocol TCP -LocalPort 4318 -Action Allow -RemoteAddress 10.0.0.0/8

On AWS, Google Cloud and Azure, also allow the port in the security group or network firewall rules; host firewalls and cloud firewalls are separate.

Port 4318 with Docker

# Publish on localhost only. Docker's port rules bypass ufw and firewalld,
# so -p 4318:4318 would expose the port to the whole network.
docker run -d -p 127.0.0.1:4318:4318 otel/opentelemetry-collector

The format is -p host_port:container_port. Containers on the same Docker network reach each other on the container port directly, without publishing it. Convert a long docker run command into a Compose file with docker run to compose.

Test port 4318 from another machine

nc -zv example.com 4318

Test-NetConnection example.com -Port 4318

Related ports

• Port 4317 (OpenTelemetry (OTLP gRPC)): used by OpenTelemetry to send traces, metrics and logs over gRPC (OTLP).
• Port 9090 (Prometheus): the default port of the Prometheus server.

More monitoring and logging ports

161 (SNMP) , 162 (SNMP traps) , 514 (Syslog) , 5601 (Kibana) , 9093 (Alertmanager / Kafka controller) , 9100 (Node exporter / printing) . See all ports in the port lookup.

Sources

• IANA port registry: 4318

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Frequently asked questions