What is the difference between polling, long polling, and WebSocket?

Question

Accepted Answer

**Polling** — client requests repeatedly. **Long Polling** — server holds request. **WebSocket** — persistent connection.

**Polling:**
- Client requests at intervals.
- Wastes bandwidth if no updates.
- Simple implementation.

```
Polling:
Client → Request → Server (every 5s)
Client ← Response ← Server
(Frequent empty responses)
```

**Long Polling:**
- Server holds request until data.
- Reduces unnecessary requests.
- Still HTTP overhead.

```
Long Polling:
Client → Request → Server (held)
Client ← Response ← Server (when data)
```

**WebSocket:**
- Persistent bidirectional connection.
- Real-time, low latency.
- More complex.

```
WebSocket:
Client ←→ Server (persistent)
(Real-time both ways)
```

**Key differences:**
- **Polling** — frequent requests.
- **Long Polling** — held request.
- **WebSocket** — persistent.

Systems Analyst: What is the difference between polling, long polling, and WebSocket?