Settings reference

SIO_ENGINEIO_PING_INTERVAL_MS

Default: 25_000

Interval, in milliseconds, between server-to-client pings.

SIO_ENGINEIO_PING_TIMEOUT_MS

Default: 20_000

Time, in milliseconds, the server waits for a pong after sending a ping before considering the connection dead.

SIO_ENGINEIO_MAX_PAYLOAD_BYTES

Default: 1_000_000

Maximum size, in bytes, of a single HTTP long-polling payload.

Engine.IO packets queued for polling are batched up to this limit. Segments that do not fit are delivered in a subsequent response.

Import-time behaviour

These settings are read once at import time by the Engine.IO implementation. They are global for the process. Per-session overrides are not currently supported.

Used by

These values are used by:

  • the Engine.IO open packet sent to clients;

  • pingInterval;

  • pingTimeout;

  • maxPayload;

  • HTTP long-polling timeout and batching;

  • WebSocket heartbeat loop.