Protocols are the precise rules that let machines communicate without intuition—anticipating every possible failure because at Internet scale, everything that can go wrong does.
The transport layer solves a problem that seems impossible: letting applications have private, reliable conversations over infrastructure that loses packets, reorders them, and knows nothing about conversations at all.
Your computer has one network connection but dozens of programs talking to the network. A socket is how each conversation stays separate—the endpoint that lets packets find exactly the right program.
TCP and UDP aren't competitors—they're answers to different questions. One asks 'Did you get that?' The other says 'I hope you got that.' Knowing which question your application is asking determines everything.
Every TCP state tells you who spoke last and what they're waiting for—which is often enough to diagnose the problem without guessing.
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