如何为阻塞调用设置超时？

Question

我有一个带多个客户端的多线程聊天服务器（每个客户端都在新线程中处理）。

如果一个客户端断开连接，服务器上相关的线程会卡住在inputstream.readLine()这个阻塞调用上。

我该如何设置某种超时时间，以便在2000毫秒没有响应时关闭套接字并释放线程？

class Handler(socket: Socket) extends Runnable {
  def run() : Unit = {
    val inputstream = new BufferedReader(new InputStreamReader(socket.getInputStream()))
    val outputstream = new BufferedWriter(new OutputStreamWriter(socket.getOutputStream()))
    var break = false
    while(break != true){
      val input = inputstream.readLine() // blocking call
// how do i time out after 2000ms?
      input match {
        case "update" =>
          outputstream.write("message")
          outputstream.newLine()
          outputstream.flush()
        case _ => // any other input, break and close socket
          break = true
      }
    }
    socket.close()
  }
}

object ChatServer extends App {
  val server = new ServerSocket(10000)
  while(true) {
    val socket = server.accept // blocking call
    (new Thread(new Handler(socket))).start()
    // some condition{
    //   server.close()
    // }
  }
}

- Gimme the 411

Answer 1

你可以使用BufferedReader.ready()：

如果下一个读取操作不会被阻塞，则返回true，否则返回false。请注意，返回false并不保证下一个读取操作将被阻塞。

class Handler(socket: Socket) extends Runnable {
  def run(): Unit = {
    val inputstream = new BufferedReader(new InputStreamReader(socket.getInputStream))
    val outputstream = new BufferedWriter(new OutputStreamWriter(socket.getOutputStream))

    var break = false
    val startTime = System.currentTimeMillis()

    while (!break) {
      if (inputstream.ready()) {
        val input = inputstream.readLine()
        input match {
          case "update" =>
            outputstream.write("message")
            outputstream.newLine()
            outputstream.flush()
          case _ => // any other input, break and close socket
            break = true
        }
      } else if (System.currentTimeMillis() - startTime >= 2000) {
        break = true
      }
    }
    socket.close()
  }
}

- Yuval Itzchakov