Connection Setup

Endpoint Configuration

The endpoint field in RealtimeClientConfig defines the broker connection parameters:

const client = new RealtimeClient({
  endpoint: {
    host: "broker.example.com",   // Broker hostname
    port: 443,                     // Broker port
    scheme: "wss",                 // "wss" (secure) or "ws"
    path: "/mqtt",                 // WebSocket path (if required by broker)
    clientId: "my-client-123",     // Unique client identifier
    username: "user",              // Auth username
    password: "token",             // Auth password / token
    cleanSession: false,           // Broker session persistence
    keepAliveSeconds: 15,          // Keep-alive interval
  },
});

Field Reference

Field	Type	Default	Description
host	string	required	Broker hostname
port	number	required	Broker port
scheme	string	"wss"	WebSocket scheme
path	string	—	WebSocket path appended to URL
clientId	string	—	Unique client identifier
username	string	—	Auth username
password	string	—	Auth password or token
cleanSession	boolean	false	Whether broker should discard previous session
keepAliveSeconds	number	15	MQTT keep-alive interval in seconds

Connection Lifecycle

Idle → Opening → Live → Closing → Idle
                   ↓
               Resuming → Live (auto-reconnect)

The SDK handles reconnection automatically. When the connection drops, it transitions to Resuming and attempts to reconnect using mqtt.js's built-in reconnection mechanism. Upon reconnection, all tracked subscriptions are restored.

Connection State

Monitor the connection state using callbacks or observables:

// Callback API
client.onStateChange((state) => {
  // LinkState: "Live" | "Opening" | "Closing" | "Idle" | "Resuming"
});

// RxJS API
client.state$.subscribe((state) => {
  console.log(state);
});