java - socket 未正确关闭

Question

我正在尝试创建一个 UDP 监听器，它将在单独的线程上监听。第一次运行正常，但是当我停止连接然后再次启动时，它给了我错误。

listenerRunnable = new Runnable() {
        public void run() {
            //This thread will listen keep listening to the UDP traffic and put it to the log source string
            try {
                sock = new DatagramSocket(portNumber);
            } catch (SocketException e1) {
                // TODO Auto-generated catch block
                e1.printStackTrace();
            }
            while(keepListening) {
                try {
                    pack = new DatagramPacket(recievedData, BUFFERSIZE);
                    sock.receive(pack);

                    String data = new String(pack.getData(), 0, pack.getLength());
                    addToLog(data);
                    System.out.println(data);
                } catch (IOException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
                sock.close();
            }
        }
    };

/**
 * Function to start the listening thread.
 */
public void startListening(int portNum) {
    keepListening = true;
    portNumber = portNum;

    listenerThread = new Thread(listenerRunnable);

    logSource_buffer = "";
    logSourcehtml_buffer = "";
    logSourcehtml_temp = "";
    ipListIndex_beg = 0;
    ipListIndex_end = -1;

    if(!listenerThread.isAlive()) {
        listenerThread.start();
    }
}

/**
 * stops the listening thead.  When the listening thread sees that keepListening is set to false
 * it will reach the end of its loop, close the socket, and the thread will die.
 */
public void stopListening() {
    keepListening = false;
}

它给了我以下错误:

logUpdatingThread has entered synchronized block!!! java.net.SocketException: Unrecognized Windows Sockets error: 0: Cannot bind at java.net.PlainDatagramSocketImpl.bind0(Native Method) at java.net.PlainDatagramSocketImpl.bind(Unknown Source)

指向带有 sock.recieve(pack); 的那一行；
似乎由于某种原因套接字没有关闭，因为我认为它在 sock.recieve(pack) 等待并且永远不会退出 while 循环来关闭套接字。不过，我将如何解决这个问题？

谢谢

Answer 1

在调用接收之前，您必须添加 setSoTimeout(timeout)。这将定期抛出 SocketTimeoutExceptions，但保持数据报套接字打开。这将允许您定期检查循环变量。

此外，您应该将循环移动到第一个 try-catch 块内并添加一个 finally 块来关闭套接字。

喜欢 :

        try {
            sock = new DatagramSocket(portNumber);
            sock.setSoTimeout(250);
            while(keepListening) {
                try {
                    pack = new DatagramPacket(recievedData, BUFFERSIZE);
                    sock.receive(pack);

                    String data = new String(pack.getData(), 0, pack.getLength());
                    addToLog(data);
                    System.out.println(data);
                } catch (IOException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
            }
        } catch (SocketException e1) {
            // TODO Auto-generated catch block
            e1.printStackTrace();
        } finally {
            sock.close();
        }