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WebSockets

Follow the HTTP upgrade handshake and the headers and status codes that establish a WebSocket connection.

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HTTP Status Codes
101 Switching Protocols
The server is switching to a different protocol as requested by the client. Learn about WebSocket upgrades and protocol negotiation.
HTTP Methods
HTTP CONNECT Method: Proxy Tunnels Explained
HTTP CONNECT opens a TCP tunnel through a proxy so HTTPS can pass untouched. See the exact request and 200 response, 407 proxy auth, and extended CONNECT.
HTTP Headers
Sec-WebSocket-Accept
Learn how the Sec-WebSocket-Accept header indicates server acceptance of a WebSocket connection upgrade. Understand the handshake process and key validation.
HTTP Headers
Sec-WebSocket-Key
Learn how the Sec-WebSocket-Key header provides a random key for WebSocket handshake validation. Understand the upgrade process and security implications.
Comparisons
SSE vs WebSockets vs Long Polling
Server-Sent Events vs WebSockets vs long polling: direction, reconnects with Last-Event-ID, the 6-connection limit and HTTP/2, and nginx proxy buffering.
HTTP Headers
Upgrade Header
Learn how the Upgrade header requests protocol upgrades to WebSocket, HTTP/2, or other protocols on the same TCP connection. Understand upgrade negotiation.
Guides
WebSockets over HTTP: Handshakes, Proxies and Auth
Trace a WebSocket HTTP handshake, verify Sec-WebSocket-Accept, configure nginx, secure browser authentication, and debug idle disconnects and close codes.

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