Exemplo de Socket em Kotlin (Server)

server.kt

import interfaces.IO

import client.entities.Client

import java.io.InputStream
import java.io.OutputStream
import java.net.ServerSocket
import java.net.Socket
import java.nio.charset.Charset
import java.util.*

fun sendMessage (outputStream: OutputStream, message: String) {

	val bufferedMessage = message.toByteArray(Charsets.UTF_8)
	outputStream.write(bufferedMessage)
	outputStream.flush()
	
}

fun receiveMessage (inputStream: InputStream): String {
	val buffer = ByteArray(4096)
	val size - inputStream.read(buffer)
	
	return buffer.copyOf(size).toString(Charsets.UTF_8)
}

fun clientHandler (client: Socket) {
	val clientWriter = client.getOutputStream() // send message to new client
	val clientReader = client.getInputStream() // receive message from new client
	
	var message = receiveMessage(clientReader)
	println(message)
	
	sendMessage(clientWriter, "O Cão Piolho")
	
}

fun main (args: Array<String>) {
	server: ServerSocket = ServerSocket(9999)
	
	while (true) {
		client: Socket = server.accept()
		
		val handlerThread = Thread {
			clientHandler(client)
		}
		
		handlerThread.start()
	}
}

Mais simples que mastigar água.