Port 9100: JetDirect
Port 9100 is raw, or JetDirect, printing, where a print job is sent directly to a network printer without a print-spooler protocol wrapping it. It is also, coincidentally, the conventional port for the Prometheus Node Exporter, so check which service you actually mean before troubleshooting.
| Port number | 9100 |
|---|---|
| Service | Raw / HP JetDirect printing |
| Protocol | TCP |
| Category | Printing |
| Default encryption | No |
How do I check whether port 9100 is open?
Port 9100 carries TCP, so a connection either completes its handshake or it does not, which makes the check definitive.
| Question | Command | What to know |
|---|---|---|
| Is it open on a remote host? | nc -vz example.com 9100 | A TCP handshake either completes or it does not, so netcat gives a definitive answer in one line. |
| Same check on Windows | Test-NetConnection example.com -Port 9100 | Built into PowerShell. TcpTestSucceeded in the output is the answer; telnet is not installed by default on modern Windows. |
| What is listening locally? | ss -tlnp | grep ':9100 ' | Lists the process bound to port 9100 on Linux. On macOS use lsof -nP -iTCP:9100 -sTCP:LISTEN, on Windows netstat -ano | findstr :9100 |
Replace example.com with the host you are testing. A blocked port and a port with nothing listening on it look identical from the outside, so if a service should be running, check locally before blaming the firewall.
Frequently asked questions
What is port 9100 used for?
Port 9100 is raw, or JetDirect, printing, where a print job is sent directly to a network printer without a print-spooler protocol wrapping it. It is also, coincidentally, the conventional port for the Prometheus Node Exporter, so check which service you actually mean before troubleshooting.
Is port 9100 TCP or UDP?
Port 9100 (JetDirect) uses TCP.
Is port 9100 secure?
Port 9100 is not encrypted by default. Where possible, use an encrypted alternative or tunnel it over TLS or a VPN.
Should I open port 9100 on my firewall?
Only if you specifically need JetDirect. Expose it to the smallest set of trusted sources, and never open database or Windows-service ports to the whole internet.