What Is Blocking IO?

Blocking IO is the model in which a read or write call does not return until the operation completes, suspending the calling thread until data is available or sent. The code is simple and sequential, but the thread does nothing useful while waiting. Handling many connections this way requires many threads or processes.

Why it matters

Blocking IO is easy to reason about and fine for sequential build scripts, but it limits how many things one thread can wait on. Recognizing it explains why concurrent workloads adopt non-blocking models instead.

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