water/server/config/mqtt.php

<?php

$subscriptions = array_filter(array_map('trim', explode(',', (string) env('MQTT_SUBSCRIPTIONS', 'devices/+/telemetry'))));
$publishTopics = array_filter(array_map('trim', explode(',', (string) env('MQTT_PUBLISH_TOPICS', 'devices/+/command'))));

return [
    // Keep MQTT disabled until a broker and credentials have been configured.
    'enabled' => filter_var(env('MQTT_ENABLED', false), FILTER_VALIDATE_BOOL),
    'address' => sprintf(
        '%s://%s:%d',
        env('MQTT_SCHEME', 'mqtt'),
        env('MQTT_HOST', '127.0.0.1'),
        (int) env('MQTT_PORT', 1883)
    ),
    'subscriptions' => array_fill_keys($subscriptions, (int) env('MQTT_SUBSCRIBE_QOS', 1)),
    'publish_topics' => $publishTopics,
    'max_payload_bytes' => (int) env('MQTT_MAX_PAYLOAD_BYTES', 1048576),
    'client' => [
        'client_id' => env('MQTT_CLIENT_ID', 'saiadmin-server'),
        'username' => env('MQTT_USERNAME', ''),
        'password' => env('MQTT_PASSWORD', ''),
        'keepalive' => (int) env('MQTT_KEEPALIVE', 50),
        'clean_session' => filter_var(env('MQTT_CLEAN_SESSION', false), FILTER_VALIDATE_BOOL),
        'reconnect_period' => (int) env('MQTT_RECONNECT_PERIOD', 3),
        'connect_timeout' => (int) env('MQTT_CONNECT_TIMEOUT', 10),
        'ssl' => filter_var(env('MQTT_SSL', false), FILTER_VALIDATE_BOOL),
    ],
];