Syntax
UPPERCASE words are placeholders to replace. Brackets in the syntax line describe optional arguments; do not type those brackets literally.
ss [-l] [-n] [-t] [-p]Example
ss -lnt
# For process ownership where permitted:
ss -lntpExpected result
Listening TCP sockets with numeric addresses and ports. -p adds process information when accessible; lack of a visible process name is not proof that no process owns the socket.
Notes and traps
ss belongs to iproute2, not Bash. -l selects listening sockets, -n keeps numbers and -t selects TCP. UDP needs -u and has different state semantics. A listener does not prove remote routing, firewall access or application health.
Try it
Compare the listener's address with the destination used by a failing client. What does a 127.0.0.1 bind tell you? What further checks follow a 0.0.0.0 listener?
Answer and reasoning
Loopback is only reachable within that host. 0.0.0.0 means all local IPv4 addresses, not proof of external reachability. Next check the actual reachable address, routes and access policy, then test the application's response.
Related commands
Related tasks may need different flags and have different semantics. Check the entry before translating a command between shells.
Official reference ↗Updated 14 September 2026. Manual reviewed 14 September 2026. Invocation with iproute2 6.1.0 returned partial output because netlink access was restricted; complete listener/process inspection was not verified. No remote reachability or firewall changes tested.