Cybersecurity Triage
Read-onlyFind Listening Ports with ss
You need to list local TCP services that are accepting connections.
Command
ss -ltnpBefore you run this
System impact: Read-only. Low when scoped to the shown target.
When not to use it: Do not assume a listening socket is externally reachable; firewall and bind address still matter.
Expected output
A table of listening TCP sockets with local addresses, ports, and associated processes when available.
System impact
Read-only. Nothing changes. The command displays listening TCP sockets.
Recovery / rollback: no state is changed.
When to use it
Use when a service should be reachable, or when you need to audit listening ports.
When not to use it
Do not assume a listening socket is externally reachable; firewall and bind address still matter.
Watch this command run
Command transcript
This sanitized transcript shows the commands and output shape without exposing host details.
$ ss -ltnp
State Recv-Q Send-Q Local Address:Port Peer Address:Port Process
LISTEN 0 511 0.0.0.0:80 0.0.0.0:* users:(("nginx",pid=1907,fd=6))
LISTEN 0 128 localhost:5432 0.0.0.0:* users:(("postgres",pid=2011,fd=7))
LISTEN 0 64 0.0.0.0:22 0.0.0.0:* users:(("sshd",pid=801,fd=3))$ ss -tan state established
State Recv-Q Send-Q Local Address:Port Peer Address:Port
ESTAB 0 0 192.0.2.10:443 198.51.100.20:51422
ESTAB 0 0 192.0.2.10:5432 192.0.2.10:41430View commands shown
These are the commands shown in the sanitized transcript.
Commands shown
ss -ltnpss -tan state established
next steps
Related commands
List Listening Ports on a VPS
Unexpected network listeners are first-response evidence.
ss -ltnp
List Listening TCP Sockets
Firewall rules matter after you know what is listening.
ss -ltnp
Find Allowed Ports with No Listener
An open firewall rule can outlive the service it was created for.
comm -23 <(ufw status numbered | awk '/ALLOW/ {print}' | grep -Eo '[0-9]+/(tcp|udp)' | cut -d/ -f1 | sort -u) <(ss -ltnp | awk '/LISTEN/ {n=split($4,a,":"); print a[n]}' | sort -u)
Check Whether Databases Listen Publicly
The fastest database security check is the listening address.
ss -ltnp | awk '$4 ~ /:(5432|3306)$/ {print}'
Find Public Listeners Not Allowed by UFW
The process was public, but the firewall did not mention it.
comm -13 <(ufw status numbered | awk '/ALLOW/ {print}' | grep -Eo '[0-9]+/(tcp|udp)' | cut -d/ -f1 | sort -u) <(ss -ltnp | awk '$4 ~ /^(0[.]0[.]0[.]0|[[]::[]]|[*]):/ {n=split($4,a,":"); print a[n]}' | sort -u)
Study mapping
Use this as independent command practice: read the notes, predict the output, then compare it with the example before using a real shell.
Useful for
- LPIC-1 style command-line practice
- LFCS style performance tasks
- Linux+ style troubleshooting review
Independent study support only. No affiliation, endorsement, exam dumps, or real exam questions.