带套接字的 Java 单实例软件。 windows下关闭socket的问题

Question

我需要强制我的 Java 应用程序以单个实例运行。我发现this link这段非常好的代码使用套接字而不是使用文件系统解决了问题。

这是我调整后的:

包 cern.ieplc.controller; 导入 java.net.InetAddress; 导入 java.net.InetSocketAddress; 导入 java.net.ServerSocket; 导入java.net.Socket； 导入 java.net.UnknownHostException;

导入org.apache.log4j.Logger;

导入java.io.BufferedReader; 导入java.io.IOException； 导入 java.io.InputStreamReader; 导入java.io.OutputStream;

public class ApplicationInstanceManager {

    public interface ApplicationInstanceListener {
        public void newInstanceCreated();
    }

    private static final Logger log = Logger.getLogger(CustomLock.class);

    private static ApplicationInstanceListener subListener;

    /** Randomly chosen, but static, high socket number */
    public static final int SINGLE_INSTANCE_NETWORK_SOCKET = 44331;

    /** Must end with newline */
    public static final String SINGLE_INSTANCE_SHARED_KEY = "$$NewInstance$$\n";

    private static ServerSocket socket;
    /**
     * Registers this instance of the application.
     *
     * @return true if first instance, false if not.
     */
    public static boolean registerInstance() {
        // returnValueOnError should be true if lenient (allows app to run on network error) or false if strict.
        boolean returnValueOnError = true;
        // try to open network socket
        // if success, listen to socket for new instance message, return true
        // if unable to open, connect to existing and send new instance message, return false
        try {
            socket = new ServerSocket(SINGLE_INSTANCE_NETWORK_SOCKET, 10, InetAddress.getByAddress(new byte[]{127,0,0,1}));
            socket.setReuseAddress(true);//allows the socket to be bound even though a previous connection is in a timeout state.
            socket.bind(new InetSocketAddress(SINGLE_INSTANCE_NETWORK_SOCKET));
            log.debug("Listening for application instances on socket " + SINGLE_INSTANCE_NETWORK_SOCKET);
            Thread instanceListenerThread = new Thread(new Runnable() {
                public void run() {
                    boolean socketClosed = false;
                    while (!socketClosed) {
                        if (socket.isClosed()) {
                            socketClosed = true;
                        } else {
                            try {
                                Socket client = socket.accept();
                                BufferedReader in = new BufferedReader(new InputStreamReader(client.getInputStream()));
                                String message = in.readLine();
                                if (SINGLE_INSTANCE_SHARED_KEY.trim().equals(message.trim())) {
                                    log.debug("Shared key matched - new application instance found");
                                    fireNewInstance();
                                }
                                in.close();
                                client.close();
                            } catch (IOException e) {
                                socketClosed = true;
                            }
                        }
                    }
                }
            });
            instanceListenerThread.start();
            // listen
        } catch (UnknownHostException e) {
            log.error(e.getMessage(), e);
            return returnValueOnError;
        } catch (IOException e) {
            log.debug("Port is already taken.  Notifying first instance.");
            try {
                Socket clientSocket = new Socket(InetAddress.getByAddress(new byte[]{127,0,0,1}), SINGLE_INSTANCE_NETWORK_SOCKET);
                OutputStream out = clientSocket.getOutputStream();
                out.write(SINGLE_INSTANCE_SHARED_KEY.getBytes());
                out.close();
                clientSocket.close();
                log.debug("Successfully notified first instance.");
                return false;
            } catch (UnknownHostException e1) {
                log.error(e.getMessage(), e);
                return returnValueOnError;
            } catch (IOException e1) {
                log.error("Error connecting to local port for single instance notification");
                log.error(e1.getMessage(), e1);
                return returnValueOnError;
            }

        }
        return true;
    }

    public static void setApplicationInstanceListener(ApplicationInstanceListener listener) {
        subListener = listener;
    }

    private static void fireNewInstance() {
        if (subListener != null) {
            subListener.newInstanceCreated();
        }
    }

    public static void closeInstance() {
        if (socket != null) {
            try {
                socket.close();
            } catch (IOException e) {
                log.error("Error while closing the socket");
            }
        }
    }
}

我尝试了该代码，它在 Linux 下运行得非常好。如果我关闭应用程序(甚至试图杀死它)，套接字将立即释放，我可以启动一个新的应用程序! 不幸的是在windows下想起来并不那么容易。资源一旦分配就永远不会释放。如果我关闭该软件，我将无法再次启动它，直到我关闭我的部分。

关于如何很好地修复代码以使其在 Windows 下运行的任何想法。 我以为我可以使用关闭钩子(Hook)来捕获至少正常的关闭。 不知道该怎么办，以防进程以意外方式终止。

这里我附上了通过 SW TCPView 完成的打印屏幕，该屏幕显示了 java 保持端口打开的方式:

我尝试实现一个更简单的版本。还是同样的问题。 windows下资源不释放。

这是第二个代码:

import java.net.ServerSocket;
import javax.swing.JOptionPane;
import javax.swing.JFrame;
import java.io.IOException;
import java.net.BindException;

class MyApplication{
    public static ServerSocket serverSocket;
    public static void main(String as[])
    {
        try
        {
            //creating object of server socket and bind to some port number
            serverSocket = new ServerSocket(15486);
            ////do not put common port number like 80 etc.
            ////Because they are already used by system
            JFrame jf = new JFrame();
            jf.setVisible(true);
            jf.setSize(200, 200);
        }
        catch (BindException exc)
        {
            JOptionPane.showMessageDialog(null, "Another instance of this application is already running.", "Error", JOptionPane.ERROR_MESSAGE);
            System.exit(0);
        }
        catch (IOException exc)
        {
            JOptionPane.showMessageDialog(null, "Another instance of this application is already running.", "Error", JOptionPane.ERROR_MESSAGE);
            System.exit(0);
        }
    }
}

有些想法没有正确关闭。 如果我也将以下代码放入关闭钩子(Hook)中，它就不起作用:

//关闭服务器

try{
    serverSocket.close();
}catch (IOException e) {
    e.printStackTrace();
}

提前致谢

Answer 1

尝试

ServerSocket socket = new ServerSocket();
socket.setReuseAddress(true);
socket.bind(new InetSocketAddress(port));

http://download.oracle.com/javase/6/docs/api/java/net/ServerSocket.html#setReuseAddress%28boolean%29

When a TCP connection is closed the connection may remain in a timeout state for a period of time after the connection is closed (typically known as the TIME_WAIT state or 2MSL wait state). For applications using a well known socket address or port it may not be possible to bind a socket to the required SocketAddress if there is a connection in the timeout state involving the socket address or port.

Enabling SO_REUSEADDR prior to binding the socket using bind(SocketAddress) allows the socket to be bound even though a previous connection is in a timeout state.