为什么客户端代码不会终止? (我们需要在运行客户端之前先启动服务器程序)套接字客户端不会终止
服务器代码:
public class ServerSocketTest {
static final int PORT = 9999;
public static void main(String[] args) throws IOException {
final ServerSocket serverSocket = new ServerSocket(PORT);
Runtime.getRuntime().addShutdownHook(new Thread() {
@Override
public void run() {
try {
serverSocket.close();
} catch (IOException e) {
e.printStackTrace();
}
}
});
while (true) {
final Socket socket = serverSocket.accept();
Runnable runnable = new Runnable() {
@Override
public void run() {
System.out.println(socket);
}
};
Thread thread = new Thread(runnable);
thread.start();
}
}
}
客户端代码:
public class SocketClient {
public static void main(String[] args) throws UnknownHostException,
IOException {
final Socket socket = new Socket("localhost", ServerSocketTest.PORT);
Runtime.getRuntime().addShutdownHook(new Thread() {
@Override
public void run() {
System.out.println("waiting to close socket ");
printThread(Thread.currentThread());
try {
socket.close();
} catch (Exception e) {
e.printStackTrace();
}
}
});
Runtime.getRuntime().addShutdownHook(new Thread() {
@Override
public void run() {
System.out.println("waiting to exit");
printThread(Thread.currentThread());
System.exit(0);
}
});
}
static void printThread(Thread currentThread) {
System.out.println(currentThread + ": Alive=" + currentThread.isAlive()
+ ",Daemon=" + currentThread.isDaemon());
}
}
我使用Ubuntu。使用JConsole,我可以跟踪以下线程加上其他一些RMI & JMX主题:
名称:指向处理器 状态:等待[email protected] 总阻塞:1总等待:2
堆栈跟踪:
java.lang.Object.wait(Native Method)
java.lang.Object.wait(Object.java:503)
java.lang.ref.Reference$ReferenceHandler.run(Reference.java:133)
名称:终结 统计E:对[email protected] 总等待阻止:1总等待:2
堆栈跟踪:
java.lang.Object.wait(Native Method)
java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:135)
java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:151)
java.lang.ref.Finalizer$FinalizerThread.run(Finalizer.java:177)
名称:信号调度 国家:RUNNABLE 总阻塞:0总等待:0
堆栈跟踪:
名称:DestroyJavaVM 状态:阻塞net.SocketClient[email protected] 总等待:0总等待:1个
堆栈跟踪:
java.lang.Object.wait(Native Method)
java.lang.Thread.join(Thread.java:1258)
java.lang.Thread.join(Thread.java:1332)
java.lang.ApplicationShutdownHooks.runHooks(ApplicationShutdownHooks.java:106)
java.lang.ApplicationShutdownHooks$1.run(ApplicationShutdownHooks.java:46)
java.lang.Shutdown.runHooks(Shutdown.java:123)
java.lang.Shutdown.sequence(Shutdown.java:167)
java.lang.Shutdown.shutdown(Shutdown.java:234)
- locked [email protected]
名称:螺纹1(这是我添加的关闭钩子调用System.exit) 状态:BLOCKED on [email protected]归属:DestroyJavaVM 总阻塞:1等待总数:0
堆栈跟踪:
java.lang.Shutdown.exit(Shutdown.java:212)
java.lang.Runtime.exit(Runtime.java:107)
java.lang.System.exit(System.java:960)
net.SocketClient$2.run(SocketClient.java:31)
名称:SIGINT处理程序(这似乎当按下Ctrl + C组合被spwaned) 状态:阻塞的java.lang。类@ 127bd04拥有者:DestroyJavaVM 总阻塞:1总等待:0
堆栈跟踪:
java.lang.Shutdown.exit(Shutdown.java:212)
java.lang.Terminator$1.handle(Terminator.java:52)
sun.misc.Signal$1.run(Signal.java:212)
java.lang.Thread.run(Thread.java:722)
你说的“客户端代码不会终止”是什么意思?看来你的客户甚至没有建立连接。 – 2012-07-21 07:14:42
似乎从任何关闭钩子调用System.exit(status)都会导致该线程与DestroyJavaVM线程之间发生死锁。在SIGINT处理程序(如果Control + C被按下)线程和DestroyJavaVM线程之间也是如此。当然,当关闭已经启动时调用System.exit(status)几乎没有意义。 – 2012-07-21 13:29:56
嗯......非常有趣。你能否请你打开你的任务管理器,看看你的客户有多少线程? – 2012-07-21 17:51:08