中断DatagramSocket.receive中的一个线程

Question

I'm building an application that listens on both TCP and UDP, and I've run into some trouble with my shutdown mechanism. When I call Thread.interrupt() on each of the listening threads, the TCP thread is interrupted from listening, whereas the UDP listener isn't. To be specific, the TCP thread uses ServerSocket.accept() , which simply returns (without actually connecting). Whereas the UDP thread uses DatagramSocket.receive() , and doesn't exit that method.

Is this an issue in my JRE, my OS, or should I just switch to (Datagram)Socket.close() ?

UPDATE: I've found an analysis of the problem. It confirms that the behavior is not consistent.

Answer 1

A common idiom for interrupting network IO is to close the channel. That would be a good bet if you need to effectively interrupt it while its waiting on sending or receiving.

public class InterruptableUDPThread extends Thread{

   private final DatagramSocket socket;

   public InterruptableUDPThread(DatagramSocket socket){
      this.socket = socket;
   }
   @Override
   public void interrupt(){
     super.interrupt();  
     this.socket.close();
   }
}

Answer 2

As far as I know, close() is the proper way to interrupt a blocked socket. Interrupting and keeping open something that may have already done a partial read or write makes things unnecessarily complex. It's easier to only have to deal with a "success" or "give up" result.

Answer 3

DatagramSocket.receive blocks until it receives a datagram. Probably what you need to do is use setSoTimeout to make it timeout.