Prometheus Node Exporter / JetDirect
What is Port 9100?
Port 9100 has two primary uses. In the Prometheus monitoring ecosystem, port 9100 is the default port for the Node Exporter, which exposes hardware and OS-level metrics from Linux and Unix systems — CPU usage, memory, disk I/O, network statistics, and filesystem information. The Node Exporter is installed on virtually every server monitored by Prometheus. Separately, port 9100 is also used by HP JetDirect (RAW printing protocol), which allows network printers to receive print jobs directly over TCP. When troubleshooting, it's important to determine which service is using the port based on context.
Common Uses
- Prometheus Node Exporter system metrics
- HP JetDirect network printing
- Infrastructure monitoring and alerting
- Print job submission to network printers
Technical Details
Copy-paste commands to check port 9100 (Prometheus Node Exporter / JetDirect) from your terminal
Test connectivity
nc -zv example.com 9100
curl -v --max-time 5 http://example.com:9100/
telnet example.com 9100
nmap -p 9100 -sV example.com
(echo > /dev/tcp/example.com/9100) 2>/dev/null && echo "open" || echo "closed"
Open port in firewall
sudo ufw allow 9100/tcp
sudo iptables -A INPUT -p tcp --dport 9100 -j ACCEPT
sudo firewall-cmd --permanent --add-port=9100/tcp && sudo firewall-cmd --reload
Security Considerations
Node Exporter exposes detailed system information. Restrict access to Prometheus servers only via firewall rules. Don't expose Node Exporter to the internet. For JetDirect printing, restrict to trusted networks. Some printers have vulnerabilities accessible through port 9100 that allow code execution or information disclosure.
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