Pusher

Channels REST API: POST /apps/{app_id}/events to trigger an event on a channel. The data model is simple: apps contain channels, events are published to channels. Channel naming conventions: public channels (any name), private channels (private-prefix), presence channels (presence-prefix), and encrypted channels (private-encrypted-prefix). Batch events: POST /apps/{app_id}/batch_events sends multiple events in one request. Channel info: GET /apps/{app_id}/channels returns occupied channels. Presence data: GET /apps/{app_id}/channels/{channel}/users returns online users. Webhook endpoints receive connection and channel events. The API is purposefully simple — agents trigger events, clients subscribe. The Channels protocol handles WebSocket lifecycle management automatically.

API errors return HTTP status codes with descriptive messages. Rate limits: message rate and connection limits vary by plan. The free tier allows 200,000 messages/day and 100 concurrent connections. 429 responses for rate limiting. The WebSocket infrastructure handles reconnection automatically on the client side — SDKs implement exponential backoff. Message ordering is guaranteed per-channel. Message persistence is not available — Channels is for real-time delivery, not message storage. If a client is disconnected when an event fires, they miss it. For agents needing message replay/history, Channels isn't the right choice (consider a message queue). The main reliability consideration: the ephemeral nature of WebSocket messaging means agents should design for message loss during client disconnections.

Pusher provides managed real-time messaging infrastructure through two products: Channels (pub/sub WebSocket messaging) and Beams (push notifications). For agents, Channels is the primary integration: agents trigger events on channels via the server-side REST API, and connected clients receive those events in real-time over WebSocket. Use cases include live dashboards, real-time notifications, collaborative features, and chat. Presence channels track which users are online — useful for agents managing real-time user status. Private channels enforce server-side authentication before subscription. Beams provides push notification delivery to iOS, Android, and Web. For agents building real-time features without managing WebSocket infrastructure, Pusher handles connection management, scaling, and reliability.

App credentials: app_id, key, secret, and cluster identify the Pusher app. Server-side API calls use HMAC signing with the app secret. Client-side connections use the app key (public). Private and presence channels require server-side authentication — the client requests a channel-specific auth token from the application server, which generates it using the Pusher secret. This ensures agents control channel access. Encrypted channels use end-to-end encryption — Pusher can't read the event data. For agents, the security model is well-designed: public channels for broadcast, private channels for authorized access, encrypted channels for sensitive data. The auth handshake adds implementation complexity but provides appropriate access control.

Documentation at pusher.com/docs covers Channels and Beams with API reference, SDK guides, and tutorials. The Channels documentation covers server-side event triggering and client-side subscription for each language. Server SDKs: Node, Python, PHP, Ruby, Go, Java, .NET. Client SDKs: JavaScript, iOS, Android, Flutter, React Native. The documentation is well-structured by product (Channels vs. Beams) and role (server vs. client). Getting started guides walk through the full flow: server triggers event, client receives it. The debug console in the dashboard shows events in real-time — valuable for development. For agents, the server-side SDK documentation and the authentication guide are the essential starting points.