An embeddable MQTT 3.1.1 / 5.0 broker: for tests, edge devices, or an app that is its own broker.

The process that creates a broker owns it; when it exits the broker stops.

{:ok, broker} = StemMqtt.Broker.new(port: 0, events: true)
:ok = StemMqtt.Broker.start(broker)
port = StemMqtt.Broker.port(broker)

Config

• :bind_address ("127.0.0.1"), :port (1883; 0 picks a free port)
• :ws_port - also serve MQTT over WebSocket
• :tls - %{port: ..., cert_pem: ..., key_pem: ..., client_ca_pem: nil}
• :allow_anonymous (true), :max_clients (0: unlimited), :max_qos (2)
• :max_retained_messages, :max_queued_per_client, :redelivery_interval_secs, :max_packet_size, :max_outbound_queue, :session_expiry_secs

Owner options, not passed to the broker:

• :events (false) - send {:stem_mqtt, broker.id, event} for {:client_connected, client_id}, {:client_disconnected, client_id, reason} and {:message_published, client_id, topic, qos}
• :auth (false) - send every CONNECT as {:stem_mqtt, broker.id, {:auth_request, id, client_id, username, password}}; answer with resolve_auth/3 within 10 seconds or it is denied
• :owner (the caller)

Unknown keys raise ArgumentError. Errors are {:error, {kind, message}} with kind one of :already_running, :io, :tls.