ConnectionState

Observable connection lifecycle state for MqttClient.

Collect MqttClient.connectionState as a kotlinx.coroutines.flow.StateFlow to observe state transitions and react to connectivity changes — including the underlying cause when a connection drops or a reconnect attempt fails.

Typical lifecycle: Disconnected → Connecting → Connected → Disconnected. When auto-reconnect is enabled and a connection drops unexpectedly: Connected → Reconnecting → Connected (or Disconnected on permanent failure).

Example — react to disconnect reasons

client.connectionState.collect { state ->
    when (state) {
        is ConnectionState.Connected -> println("Online")
        is ConnectionState.Connecting -> println("Connecting...")
        is ConnectionState.Reconnecting -> println("Reconnecting (attempt ${state.attempt})")
        is ConnectionState.Disconnected -> when (val reason = state.reason) {
            null -> println("Offline")
            else -> println("Offline: ${reason.reasonCode} — ${reason.message}")
        }
    }
}

Migration from 0.1.x

In 0.1.x ConnectionState was an enum with CONNECTING/CONNECTED/DISCONNECTED/ RECONNECTING constants. Replace equality checks (state == ConnectionState.CONNECTED) with is checks (state is ConnectionState.Connected).

Inheritors