UDP listener and broadcast message to main Activity - android-activity

Question

I have an android app with MainActivity.
I have succesfully deployed a BroadCastReceiver and I can receive messages.
Now I have another class that listens for new UDP messages on specific port. I would like to pass the received messages to my MainActivity so I could update some values here.
For some reason I cannot make BroadCasting from this class.
Here is the code:
MainActivity.kt
#RequiresApi(Build.VERSION_CODES.LOLLIPOP)
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
//hide top bar
supportActionBar?.hide()
//register broadcastreceiver
registerReceiver(mPlugInReceiver, getIntentFilter())
Log.d(TAG, "Registered broadcastreceiver")
//sending test message to broadcastreceiver, this works
val intent = Intent()
intent.action = "MESSAGE_RECEIVED"
intent.putExtra("MESSAGE_STRING", "sending test message to broadcastreceiver")
sendBroadcast(intent)
//start UDP server
val udpServer = udpServer()
Thread(udpServer).start()
}
udpServer.kt
class udpServer : Runnable {
private val UDP_PORT = 58651
override fun run() {
var run = true
Log.d(MainActivity.TAG, "udpServer started")
while (run) {
try {
val udpSocket = DatagramSocket(UDP_PORT)
val message = ByteArray(8000)
val packet = DatagramPacket(message, message.size)
//Log.i(MainActivity.TAG, "UDP server about to wait to receive")
udpSocket.receive(packet)
val text = String(message, 0, packet.length)
//Log.d(MainActivity.TAG, text)
//This does not work
val intent = Intent()
intent.action = "MESSAGE_RECEIVED"
intent.putExtra("MESSAGE_STRING", "sending test message to broadcastreceiver")
//This throws error: "create function 'sendBroadcast'"
sendBroadcast(intent)
} catch (e: IOException) {
//Log.e(MainActivity.TAG, "error: ", e)
//run = false
}
}
}
}
I tried to use companion object to pass data, but it doesn't work either.