import java.net.{DatagramPacket, InetAddress, MulticastSocket, SocketTimeoutException}
import java.lang.{Runnable, Thread}

object TestUdpServer {
  class UdpServer(val address: String, val port: Int, val info: String) {
    val socket = new MulticastSocket(port)
    val multicastAddressGroup = InetAddress.getByName(address)
    socket.joinGroup(multicastAddressGroup)

    def execute: Unit = {
      while(true){
        val buffer = Array.ofDim[Byte](1024)
        val data = new DatagramPacket(buffer, buffer.length)
        try{
          socket.receive(data)
          checkMessage(new String(data getData).trim, info)
        }catch{
          case e:SocketTimeoutException => // nothing
        }
      }
    }

    private def checkMessage(msg: String, info: String): Unit = {
      if(msg == "QUERY") sendReply(info)
    }
    private def sendReply(info: String): Unit = {
      log("send reply")
      val response = ("REPLY:test-server:"+info+"++").getBytes
      socket.send(new DatagramPacket(response, response.length, multicastAddressGroup, port))
    }
    def log(msg: String): Unit = println("SERVER: " + msg)
  }

  def main(args: Array[String]): Unit = {
    new UdpServer("224.0.0.1",1234, args(0)).execute
  }
}