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#sockets (4)

Cheat sheets (4)

lsof & ss — Open Files and Sockets

Diagnose what's holding a port, which files a process has open, and the state of every TCP/UDP socket using lsof and the modern iproute2 ss utility.
lsof ss lsfd sockets networking processes debug cli sysadmin web-researched

ps, ss & netstat — Processes & Sockets

Inspect running processes (ps), list network connections and listening ports (ss / netstat). Covers output formats, filtering, process trees, and socket state analysis.
ps netstat ss processes networking sockets cli sysadmin web-researched

systemd Unit Files

Writing, enabling, and managing systemd service, timer, and socket units.
systemd linux services daemons timers sockets sandboxing sysadmin web-researched

Networking Stack — OSI/TCP-IP, Sockets, TCP/UDP, MTU, NAT, DNS

How packets actually move: the OSI and TCP/IP layer models, the BSD socket API, TCP vs UDP, the three-way handshake, MTU/MSS, NAT and port translation, basic IP routing, and the full DNS resolution flow.
networking osi tcp-ip sockets tcp udp mtu nat routing dns sysadmin