Heartbeats - Predict API (Beta)

The server keeps connections alive with a heartbeat the client must answer.

Server probe — every 15 seconds the server sends a heartbeat message carrying the current epoch-millisecond timestamp:

{ "type": "M", "topic": "heartbeat", "data": 1736696400000 }

The first heartbeat arrives about 15 seconds after the connection opens.

Client response — before the next probe (within ~15 seconds), the client must echo the exact timestamp back:

{ "method": "heartbeat", "data": 1736696400000 }

The heartbeat response has no requestId and no params.

The data value must match the timestamp from the most recent server probe. A missing, stale, or mismatched value is treated as no response, and the server closes the connection on the next probe.

Clients should reconnect with backoff and re-subscribe to their topics after any disconnect.