Publish and subscribe to device events using the Particle Device Cloud API and webhooks

Steps

1. In Particle firmware, call Particle.publish("temperature", String(reading), PRIVATE) to emit a named event to the Particle Cloud; events have a max payload of 1024 bytes and are rate-limited to 1 event per second per device by default
2. Subscribe to device events from another device with Particle.subscribe("temperature", handlerFunction, MY_DEVICES) or use the Server-Sent Events (SSE) REST stream: GET https://api.particle.io/v1/devices/events?access_token=<TOKEN> to receive all events in real time
3. Create a webhook in the Particle Console or via POST https://api.particle.io/v1/integrations specifying the event name trigger, target URL, HTTP method, and optional request body template using Mustache placeholders like {{PARTICLE_EVENT_VALUE}}
4. The webhook fires when the matching event is published; Particle Cloud sends a hook-sent event confirming dispatch and a hook-response event containing the HTTP status and response body from the target URL — subscribe to these to debug webhook delivery
5. Use the REST API to query device status: GET https://api.particle.io/v1/devices/<deviceId>?access_token=<TOKEN> returns the device's online state, last heard timestamp, firmware version, and variables; call a function with POST /v1/devices/<deviceId>/<functionName>
6. Implement error handling for webhook failures: Particle Cloud uses adaptive retry with backoff when the target URL returns 4xx or 5xx responses; after repeated failures it temporarily pauses webhook delivery to protect the receiving server