Learn to inspect sockets and verify connectivity quickly using the `ss` utility on Linux. 16.11.2025 | reading time: 2 min When a service seems unreachable, `ss` gives a fast, kernel-backed view of sockets so he can discover listening ports, established peers, and the owning process in seconds. Quick server check Try these commands to see listening sockets and active TCP connections: ```shell ss -tuln Netid State Recv-Q Send-Q Local Address:Port Peer Address:Port tcp LISTEN 0 128 0.0.0.0:22 0.0.0.0:* tcp LISTEN 0 128 127.0.0.1:631 0.0.0.0:* udp UNCONN 0 0 0.0.0.0:68 0.0.0.0:* ``` And to inspect who holds an established TCP session: ```shell ss -tnp state established Netid State Recv-Q Send-Q Local Address:Port Peer Address:Port Process tcp ESTAB 0 0 192.0.2.10:22 198.51.100.5:51324 users:(("sshd",pid=1023,fd=3)) ``` Filters and flags to wield Use `-t`, `-u`, `-l`, `-a` and `-n` to narrow protocols, show listening sockets and avoid name resolution; add `-p` to reveal PIDs, `-s` for a summary, `-o` to see timer info, `-m` for memory usage and `-4`/`-6` for IP family filtering, or apply `state` filters like `state established` for quick diagnosis. When other tools help `ss` is great for kernel socket inspection, but combine it with `lsof` to see open files, `tcpdump` to capture packets, or `nmap` to test from a remote host when he needs deeper packet-level or external reachability checks. Final note Mastering `ss` will speed up troubleshooting and service validation on any Linux host; to turn practical skill into certification-ready knowledge, explore deeper topics and consider exam preparation like CompTIA Linux+ or LPIC-1 with intensive courses at bitsandbytes.academy. Join Bits & Bytes Academy First class LINUX exam preparation. network utilities troubleshooting
