Port 9100 (node_exporter / printer raw (JetDirect))

Two very common uses: Prometheus node_exporter serves host metrics on 9100, and network printers accept raw print jobs (HP JetDirect / PDL datastream, the IANA assignment) on 9100.

Registered (user) port, 1024-49151 TCP Monitoring and logging Do not expose to the internet

What port 9100 is used for

Two very common uses: Prometheus node_exporter serves host metrics on 9100, and network printers accept raw print jobs (HP JetDirect / PDL datastream, the IANA assignment) on 9100.

Security: should port 9100 be open?

Do not expose to the internet. Neither should be public. Exposed printers on 9100 accept any job and PJL commands (hackers have printed messages on thousands of printers this way); exposed node_exporter leaks system details.

IANA assignment

Service nameProtoDescriptionAssigneeReference

hp-pdl-datastr TCP PDL Data Streaming Port Shivaun Albright -

pdl-datastream TCP Printer PDL Data Stream
The protocol name "pdl-datastream" is primarily registered for use in DNS SRV records ([RFC 2782]). DNS SRV records allow a protocol to run on any port number, but the default port for this protocol is 9100. Stuart Cheshire 4 -

hp-pdl-datastr UDP PDL Data Streaming Port Shivaun Albright -

pdl-datastream UDP Printer PDL Data Stream
The protocol name "pdl-datastream" is primarily registered for use in DNS SRV records ([RFC 2782]). DNS SRV records allow a protocol to run on any port number, but the default port for this protocol is 9100. Stuart Cheshire 4 -

Registry dates for this port: registered 2002-04.

Check what is listening on port 9100

Linux: is anything listening on TCP 9100?

sudo ss -tlnp 'sport = :9100'

Linux / macOS: which process owns the port

sudo lsof -nP -i :9100

Older Linux / BSD (net-tools)

sudo netstat -tlnp | grep ':9100 '

Windows (Command Prompt)

netstat -ano | findstr :9100

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 9100 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine

nc -vz -w 5 HOST 9100

From Windows

Test-NetConnection HOST -Port 9100

Block port 9100 in the firewall

ufw

sudo ufw deny 9100/tcp

iptables

sudo iptables -A INPUT -p tcp --dport 9100 -j DROP

nftables

sudo nft add rule inet filter input tcp dport 9100 drop

Windows Firewall

New-NetFirewallRule -DisplayName 'Block TCP 9100' -Direction Inbound -Protocol TCP -LocalPort 9100 -Action Block

All port numbers · Open port checker
Assignment data: IANA port number registry (public domain), retrieved 2026-11-10.