Choosing Socket.io Transports: WebSocket vs. HTTP Long-Polling
A technical guide on choosing between WebSocket and HTTP long-polling in Socket.io, focusing on the trade-offs between network compatibility and server performance.
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Diagnosing Socket.io Transport Fallbacks: Moving from Polling to WebSockets
Learn how to diagnose and fix Socket.io connection issues where clients fall back to HTTP long-polling instead of using WebSockets, including Nginx and load balancer configurations.
nginxDiagnosing Socket.io Transport Failures: When WebSockets Fail to Upgrade
Learn how to diagnose and fix Socket.io connection issues where clients stay stuck in HTTP polling mode instead of upgrading to WebSockets, including proxy configurations and CORS fixes.
Socket.IO server pingTimeout shorter than client reconnectionDelayMax causes premature disconnects
Socket.IO's server-side pingTimeout and pingInterval govern heartbeat detection, while the client's reconnectionDelayMax caps exponential backoff during reconnection attempts. When pingTimeout is configured below reconnectionDelayMax, the server may terminate a connection before the client's backoff reaches its maximum, creating a race between server-side cl
Socket.IO JWT middleware token expiration handling on reconnection
The default @socket.io/jwt middleware validates a JWT only during the initial handshake. In Socket.IO v4.x the connection remains open after the token expires unless the server explicitly re‑validates on each reconnection or per message. Because the middleware does not enforce a maximum token lifetime beyond the handshake, a client with an expired token can
"Session ID unknown" (HTTP 400) during rolling deploys: sticky sessions vs Redis adapter for Socket.IO
I'm planning a zero-downtime migration of a small Socket.IO application to a multi-node setup behind a load balancer. During rolling restarts, clients using the default transports can hit the Engine.IO error Session ID unknown (HTTP 400), because the handshake session lives in memory on the node that issued it and a subsequent polling request may land on a d