Connections

TCP builds reliable connections. UDP does not bother. Ports identify services. Sockets tie it all together. See every connection the kernel is tracking.

Labs in this module

TCP vs UDP - TCP is a conversation. UDP is a shout. ss shows you both, live, right now.
The TCP Handshake - SYN, SYN-ACK, ACK. Three packets before a single byte of data. Watch the handshake happen in real time.
Ports and Sockets - A socket is IP plus port plus protocol. /proc/net/tcp is the kernel connection spreadsheet, in hex.
TCP States - Every TCP connection moves through a series of states. ss shows you where each connection is in its lifecycle. This is how you diagnose brok
TCP Tuning - The kernel exposes dozens of TCP tuning knobs via sysctl. Buffer sizes, keepalive timers, backlog queues. This is what SREs adjust on produc