Port 9093: Alertmanager / Kafka controller

What uses port 9093

Prometheus Alertmanager receives alerts on 9093 and routes them to email, Slack, PagerDuty or webhooks after grouping and silencing. In Kafka clusters running KRaft, 9093 is a common choice for the controller listener.

Should port 9093 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 9093

sudo ss -ltnp 'sport = :9093'

sudo lsof -nP -iTCP:9093 -sTCP:LISTEN

Get-NetTCPConnection -LocalPort 9093 -State Listen
netstat -ano | findstr :9093

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 9093

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:9093 -sTCP:LISTEN)

Stop-Process -Id (Get-NetTCPConnection -LocalPort 9093 -State Listen).OwningProcess

Allow port 9093 from trusted networks only

The examples allow 9093 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 9093 proto tcp
# Close it again:
sudo ufw delete allow from 10.0.0.0/8 to any port 9093 proto tcp

sudo firewall-cmd --permanent --add-rich-rule='rule family="ipv4" source address="10.0.0.0/8" port port="9093" protocol="tcp" accept'
sudo firewall-cmd --reload

New-NetFirewallRule -DisplayName "Alertmanager / Kafka controller 9093/TCP" -Direction Inbound -Protocol TCP -LocalPort 9093 -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 9093 with Docker

# Publish on localhost only. Docker's port rules bypass ufw and firewalld,
# so -p 9093:9093 would expose the port to the whole network.
docker run -d -p 127.0.0.1:9093:9093 prom/alertmanager

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 9093 from another machine

nc -zv example.com 9093

Test-NetConnection example.com -Port 9093

Related ports

• Port 9090 (Prometheus): the default port of the Prometheus server.
• Port 9092 (Apache Kafka): the default broker port of Apache Kafka.
• Port 9100 (Node exporter / printing): used by Prometheus node_exporter and by raw network printing (JetDirect).

More monitoring and logging ports

161 (SNMP) , 162 (SNMP traps) , 514 (Syslog) , 4317 (OpenTelemetry (OTLP gRPC)) , 4318 (OpenTelemetry (OTLP HTTP)) , 5601 (Kibana) . See all ports in the port lookup.

Sources

• IANA port registry (not registered for this use)

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Frequently asked questions