Scala(java)におけるソケット通信プログラムの処理順について

前提・実現したいこと

ScalaとScalaFXを使用したソケット通信オセロプログラミングを作成しています。
ソケット通信自体はうまくいきましたが、通信後のオセロを盤面に描画する際に思った通りの動作をしなくて困っています。

発生している問題・エラーメッセージ

ソケット通信がサーバー・クライアント間で完了したのち、お互いにメッセージのやりとりをして、そのメッセージに沿って黒丸or白丸を描画する際に、即座に描画したいのですが、自分の盤面をクリックした際に、相手からの応答があってから相手の円と自分の円が同時に描画されます。これを即座に描画するようにしたいです。

該当のソースコード

Scala 2.12.7

OseloContoroller.scala

package gui

import java.net.Socket

import scalafx.Includes._
import scalafx.scene.input.MouseEvent
import scalafx.scene.paint.Color._
import scalafx.scene.layout.GridPane
import scalafxml.core.macros.sfxml
import javafx.scene.shape.Circle
import scalafx.scene.paint.Color
import network._
import scalafx.scene.control.Button


@sfxml
class OseloController(val board: GridPane, val connecteButton: Button, val serverButton: Button){
  val server: Server = new Server(8000, board)
  var client: Client = _
  var flag: Boolean = _ //白黒の順番判定trueが黒、falseが白
  var posX:Int = _
  var posY:Int = _

  serverButton.onMouseClicked = (_: MouseEvent) =>{
    server.createServer
    flag = true
  }

  connecteButton.onMouseClicked = (_: MouseEvent) =>{
    val sc: Socket = new Socket("127.0.0.1", 8000)
    client = new Client(sc, board)
    flag = false
    client.createClient()
    client.receiveMsg()
  }


  board.onMouseClicked = (e:MouseEvent) => {
    posX = (e.x / 53).asInstanceOf[Int]
    posY = (e.y / 53).asInstanceOf[Int]
    if(flag) {
      server.sendMsg(posX.toString + "," + posY.toString)
      server.receiveMsg()
    }else{
      client.sendMsg(posX.toString + "," + posY.toString)
      client.receiveMsg()
    }
  }

}

Server.scala

package network

import java.io._
import java.net._

import javafx.scene.shape.Circle
import scalafx.scene.layout.GridPane
import scalafx.scene.paint.Color
import scalafx.scene.paint.Color._

class Server(val port: Int, val board: GridPane) extends Thread{
  var ss: ServerSocket = _
  var sc: Socket = _
  var br: BufferedReader = _
  var pw: PrintWriter = _
  var clientMsg: String = _
  var arr: Array[String] = _

  def createServer: Unit ={
    try{
      ss = new ServerSocket(port)
      println("Waiting For・・・")
      sc = ss.accept()
      println("Welcome!!")
      //以下、メッセージやり取りのための変数初期化
      try {
        br = new BufferedReader(new InputStreamReader(sc.getInputStream))
        pw = new PrintWriter(new BufferedWriter(new OutputStreamWriter(sc.getOutputStream)))
      }catch {
        case e: Exception => e.printStackTrace
      }

    } catch {
      case e:Exception => e.printStackTrace
      ss.close()
    }
  }

   def createCircle(posX: Int, posY: Int, color: Color): Unit ={
    println("Server:" + posX + "," + posY)
    board.add(new Circle(0,0,27,color), posX , posY)
  }

  def sendMsg(msg: String): Unit = {
    arr = msg.split(",")
    pw.println(msg)
    pw.flush()
    createCircle(arr(0).toInt, arr(1).toInt, Black)
  }

  def receiveMsg(): Unit ={
    while((clientMsg = br.readLine()) == null){Thread.sleep(100)}
    println(clientMsg)
    arr = clientMsg.split(",")
    createCircle(arr(0).toInt, arr(1).toInt, White)
  }

}

Client.scala

package network

import java.io._
import java.net._
import java.util._

import javafx.scene.shape.Circle
import scalafx.scene.paint.Color._
import scalafx.scene.layout.GridPane
import scalafx.scene.paint.Color

class Client(val sc: Socket, val board: GridPane){
  var br: BufferedReader = _
  var pw: PrintWriter = _
  var serverMsg: String = _
  var arr: Array[String] = _

  def createClient(): Unit ={
    try {
      br = new BufferedReader(new InputStreamReader(sc.getInputStream))
      pw = new PrintWriter(new BufferedWriter(new OutputStreamWriter(sc.getOutputStream)))
    }catch {
      case e: Exception => e.printStackTrace
    }
  }

  def createCircle(posX: Int, posY: Int, color: Color): Unit ={
    println("Client:" + posX + "," + posY)
    board.add(new Circle(0,0,27,color), posX , posY)
  }

  def sendMsg(msg: String): Unit = {
    arr = msg.split(",")
    pw.println(msg)
    pw.flush()
    createCircle(arr(0).toInt, arr(1).toInt, White)
  }

  def receiveMsg(): Unit ={
    while((serverMsg = br.readLine()) == null){Thread.sleep(100)}
    println(serverMsg)
    arr = serverMsg.split(",")
    createCircle(arr(0).toInt, arr(1).toInt, Black)
  }

}