how can i get mqtt broker server ip address?

Question

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(R.layout.activity_main)
    val client = MqttClient("tcp://(how can i get address!!!!!!!!)","test",MemoryPersistence())
    client.connect()
}

I'm trying to build a simple mqtt application using mosquitto as a broker. But I need to get an ip address, but I don't know how the heck to get it. I am trying to use the address of the wifi currently in use, but Connection is refused. What the hell am I supposed to do? No matter how much I search, I don't know how. You shouldn't even have to edit mosquitto.conf .

I've tried most of the methods found on Google. subscribe on mosquitto

Publishing on Android

I want to check if the terminal works properly.