WebSocket: ментальная модель

Question

Accepted Answer

WebSocket — persistent full-duplex pipe после HTTP upgrade. Правильный tool для bidirectional real-time; reconnect, heartbeat, auth, scaling — на вас.

## Разбор

HTTP — **half-duplex request/response**: client asks, server answers, done. «Server tells me things» через poll — wasteful, laggy. WebSocket — **long-lived pipe both ends write anytime.**

```
HTTP polling                    WebSocket
────────────                    ─────────
C → "anything new?"  (req)      C ══════════════ S   ← one open pipe
S ← "no"             (res)      C → msg          →   ← either side
C → "anything new?"  (req)      C ←          msg     ← pushes freely,
S ← "no"  (repeat forever)      C → msg  ←   msg     ← any time
```

WebSocket **starts as HTTP.** `GET` + `Upgrade: websocket` → `101 Switching Protocols` → same TCP speaks WebSocket framing. Works on 80/443 through most proxies.

## Итог

WebSocket = upgrade from HTTP to cheap duplex frames; ownership of reliability layer — yours.