Lesson 09 · 11 min
Real time: polling, SSE, WebSocket
HTTP is a question and an answer. What if the server wants to speak first?
11 minLesson 9 of 9Practice includedAsk AI on any point
Plain HTTP doesn't let the server write to the client without a request. There are three approaches. Polling — the client asks every five seconds "anything new?": simple, but wastes requests. SSE (Server-Sent Events) — one long HTTP response of type text/event-stream that the server keeps appending events to; server to client only. WebSocket — a persistent two-way connection for chats, games, and collaborative editing.
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