在我的web应用程序中，websocket通信有问题。有时，当我尝试向多个客户机发送消息时（通常我们有30-40个客户机），应用程序就会卡住。查看日志文件，似乎所有内容都挂在“broadcastmessage”方法上（在该方法中，我使用了同步锁）。
下面是这些类的实现。
websocket：

import java.io.IOException;
import java.util.Collections;
import java.util.HashSet;
import java.util.Set;

import javax.websocket.OnClose;
import javax.websocket.OnMessage;
import javax.websocket.OnOpen;
import javax.websocket.Session;
import javax.websocket.server.ServerEndpoint;

@ServerEndpoint("/websocket")
public class WebSocketServer
{
    private static Set<Session> clients = Collections.synchronizedSet(new HashSet<Session>());

    @OnMessage
    public void onMessage(String message, Session session) throws IOException, InterruptedException
    {
        if (message.equals("ping"))
        {
            session.getBasicRemote().sendText("pong");
        }
    }

    @OnOpen
    public void onOpen(Session session)
    {
        clients.add(session);
    }

    @OnClose
    public void onClose(Session session)
    {
        clients.remove(session);
    }

    public static void broadcastMessage(String message) throws IOException, InterruptedException
    {
        broadcastMessage(message, null);
    }

    private static void broadcastMessage(String message, Session session) throws IOException, InterruptedException
    {
        synchronized (clients)
        {
            for (Session client : clients)
            {
                if (session == null || !client.equals(session))
                {
                    client.getBasicRemote().sendText(message);
                }
            }
        }
    }
}

然后我在服务器启动时安排了一个servlet，它安排了一个线程（每秒钟）：

import java.io.IOException;
import java.util.Date;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class MyServlet extends HttpServlet
{
    private static final long serialVersionUID = 5064961381596268407L;

    @Override
    public void init() throws ServletException
    {
        Long period = Long.parseLong(1000);
        new MyThread().schedule(new Date(), period);
    }

    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
    {
    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
    {
    }
}

这是线程：

import java.io.File;
import java.util.Arrays;
import java.util.Comparator;
import java.util.Date;
import java.util.Timer;
import java.util.TimerTask;

import org.apache.log4j.Logger;

public class MyThread
{
    private static Timer timer;
    private String PATH = "C:\\Users\\administrator\\Pictures";
    private Logger log = Logger.getLogger("pic");

    public void schedule(Date date, Long period)
    {
        if (timer != null)
        {
            timer.cancel();
        }
        timer = new Timer();

        if (date == null)
        {
            date = new Date();
        }

        if (period != null)
        {
            timer.schedule(new ThreadLogger(), date, 1000 * period.longValue());
        }
        else
        {
            timer.schedule(new ThreadLogger(), date);
        }
    }

    public class ThreadLogger extends TimerTask
    {
        public void run()
        {
            log.debug("MyThread.run ===========================================================");
            log.debug("Directory => " + PATH);

            File dir = new File(PATH);

            FileFilterDateIntervalUtils filter = new FileFilterDateIntervalUtils(new Date());
            File[] files = dir.listFiles(filter);

            if (files != null && files.length > 0)
            {
                Arrays.sort(files, new Comparator<File>()
                {
                    public int compare(File f1, File f2)
                    {
                        return Long.valueOf(f2.lastModified()).compareTo(f1.lastModified());
                    }
                });

                try
                {
                    log.debug("Found file => " + files[0].getName());
                    WebSocketServer.broadcastMessage(files[0].getName());
                }
                catch (Exception e)
                {
                    log.error("Error: " + e.getMessage(), e);
                }
            }
            else
            {
                log.debug("Alert: 0 files");
            }

            log.debug("================================================================================");
        }
    }
}

websocket的方法broadcastmessage仅由调度线程调用！每个客户端每分钟发送一条ping消息。
你知道应用程序为什么会卡住吗？我该怎么解决？
谢谢！