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Long Polling & Real-Time HTTP

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Real-time HTTP before WebSockets

Before WebSockets (2011), browsers could only make requests — not receive pushes. Developers needed real-time features anyway: chat, live updates, collaborative editing. The solution was long polling: a client technique that simulates push by keeping an HTTP request open until the server has something to send.

Understanding long polling explains why WebSockets were so significant and why Socket.io still falls back to it.

Packets in motion — click to inspect:

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