Java 新ObjectInputStream导致挂起/超时

我知道这个问题已经被问过好几次了。然而，在所有其他问题上遵循建议之后，我仍然无法确定问题可能是什么

我有一个服务器和一个客户端。一个简单的乒乓球节目。在运行服务器和客户端并给它一些时间来运行它的进程之后，超时异常开始时不时地抛出

超时是为了防止阻塞，但是，如果删除，它将导致程序暂停

有没有办法防止这种情况发生

Server.java

public static void main(String args[]) {
        try {
            ServerSocket serverSocket = new ServerSocket(3000);
            while (true) {
                Socket socket = serverSocket.accept();
                String message = null;
                try {
                    socket.setSoTimeout(3000);
                    try (ObjectInputStream objectInputStream = new ObjectInputStream(socket.getInputStream())) {
                        message = (String) objectInputStream.readObject();
                        System.out.println("Server received " + message);
                    }
                    socket.close();
                } catch (IOException | ClassNotFoundException ex) {
                    //This exception is thrown because it hangs, but why does it hang?
                    Logger.getLogger(Server.class.getName()).log(Level.SEVERE, null, ex);
                }
                if ((message != null) && (message.equals("Ping"))) {
                    try {
                        Socket pongSocket = new Socket("localhost", 3000);
                        pongSocket.setSoTimeout(3000);
                        try (ObjectOutputStream objectOutputStream = new ObjectOutputStream(pongSocket.getOutputStream())) {
                            objectOutputStream.writeObject("Pong");
                            objectOutputStream.flush();
                            System.out.println("Server sent Pong");
                        }
                        pongSocket.close();
                        continue;
                    } catch (IOException ex) {
                        Logger.getLogger(Server.class.getName()).log(Level.SEVERE, null, ex);
                    }
                }
            }
        } catch (IOException ex) {
            Logger.getLogger(Server.class.getName()).log(Level.SEVERE, null, ex);
        }
    }

public static void main(String args[]) {
        while (true) {
            try {
                Socket pingSocket = new Socket("localhost", 3000);
                pingSocket.setSoTimeout(3000);
                try (ObjectOutputStream objectOutputStream = new ObjectOutputStream(pingSocket.getOutputStream())) {
                    objectOutputStream.writeObject("Ping");
                    System.out.println("Client sent Ping");
                    objectOutputStream.flush();
                }
                pingSocket.close();
            } catch (IOException ex) {
                Logger.getLogger(Client.class.getName()).log(Level.SEVERE, null, ex);
            }
        }
    }

public static void main(String args[]) {
    try {
        ServerSocket serverSocket = new ServerSocket(3000);
        while (true) {
            Socket socket = serverSocket.accept();
            socket.setSoTimeout(250);
            String message = null;
            ObjectOutputStream objectOutputStream = new ObjectOutputStream(socket.getOutputStream());
            ObjectInputStream objectInputStream = new ObjectInputStream(socket.getInputStream());
            try {
                message = (String) objectInputStream.readObject();
                System.out.println("server read: " + message);
            } catch (IOException | ClassNotFoundException ex) {
                Logger.getLogger(Server.class.getName()).log(Level.SEVERE, null, ex);
            }
            if ((message != null) && (message.equals("Ping"))) {
                try {
                    objectOutputStream.writeObject("Pong");
                    System.out.println("server sent pong");
                } catch (IOException ex) {
                    Logger.getLogger(Server.class.getName()).log(Level.SEVERE, null, ex);
                }
            }
            objectInputStream.close();
            objectOutputStream.close();
            socket.close();
        }
    } catch (IOException ex) {
        Logger.getLogger(Server.class.getName()).log(Level.SEVERE, null, ex);
    }
}

public static void main(String args[]) {
    while (true) {
        try {
            Socket socket = new Socket("localhost", 3000);
            String message;
            socket.setSoTimeout(250);
            ObjectOutputStream objectOutputStream = new ObjectOutputStream(socket.getOutputStream());
            objectOutputStream.writeObject("Ping");
            System.out.println("client sent ping");
            try (ObjectInputStream objectInputStream = new ObjectInputStream(socket.getInputStream())) {
                message = (String) objectInputStream.readObject();
                System.out.println("client read: " + message);
            }
            objectOutputStream.close();
            socket.close();
        } catch (IOException | ClassNotFoundException ex) {
            Logger.getLogger(Client.class.getName()).log(Level.SEVERE, null, ex);
        }
        try {
            Thread.sleep(10000);
        } catch (InterruptedException ex) {
            Logger.getLogger(Client.class.getName()).log(Level.SEVERE, null, ex);
        }
    }
}

Client.java

public static void main(String args[]) {
        try {
            ServerSocket serverSocket = new ServerSocket(3000);
            while (true) {
                Socket socket = serverSocket.accept();
                String message = null;
                try {
                    socket.setSoTimeout(3000);
                    try (ObjectInputStream objectInputStream = new ObjectInputStream(socket.getInputStream())) {
                        message = (String) objectInputStream.readObject();
                        System.out.println("Server received " + message);
                    }
                    socket.close();
                } catch (IOException | ClassNotFoundException ex) {
                    //This exception is thrown because it hangs, but why does it hang?
                    Logger.getLogger(Server.class.getName()).log(Level.SEVERE, null, ex);
                }
                if ((message != null) && (message.equals("Ping"))) {
                    try {
                        Socket pongSocket = new Socket("localhost", 3000);
                        pongSocket.setSoTimeout(3000);
                        try (ObjectOutputStream objectOutputStream = new ObjectOutputStream(pongSocket.getOutputStream())) {
                            objectOutputStream.writeObject("Pong");
                            objectOutputStream.flush();
                            System.out.println("Server sent Pong");
                        }
                        pongSocket.close();
                        continue;
                    } catch (IOException ex) {
                        Logger.getLogger(Server.class.getName()).log(Level.SEVERE, null, ex);
                    }
                }
            }
        } catch (IOException ex) {
            Logger.getLogger(Server.class.getName()).log(Level.SEVERE, null, ex);
        }
    }

public static void main(String args[]) {
        while (true) {
            try {
                Socket pingSocket = new Socket("localhost", 3000);
                pingSocket.setSoTimeout(3000);
                try (ObjectOutputStream objectOutputStream = new ObjectOutputStream(pingSocket.getOutputStream())) {
                    objectOutputStream.writeObject("Ping");
                    System.out.println("Client sent Ping");
                    objectOutputStream.flush();
                }
                pingSocket.close();
            } catch (IOException ex) {
                Logger.getLogger(Client.class.getName()).log(Level.SEVERE, null, ex);
            }
        }
    }

public static void main(String args[]) {
    try {
        ServerSocket serverSocket = new ServerSocket(3000);
        while (true) {
            Socket socket = serverSocket.accept();
            socket.setSoTimeout(250);
            String message = null;
            ObjectOutputStream objectOutputStream = new ObjectOutputStream(socket.getOutputStream());
            ObjectInputStream objectInputStream = new ObjectInputStream(socket.getInputStream());
            try {
                message = (String) objectInputStream.readObject();
                System.out.println("server read: " + message);
            } catch (IOException | ClassNotFoundException ex) {
                Logger.getLogger(Server.class.getName()).log(Level.SEVERE, null, ex);
            }
            if ((message != null) && (message.equals("Ping"))) {
                try {
                    objectOutputStream.writeObject("Pong");
                    System.out.println("server sent pong");
                } catch (IOException ex) {
                    Logger.getLogger(Server.class.getName()).log(Level.SEVERE, null, ex);
                }
            }
            objectInputStream.close();
            objectOutputStream.close();
            socket.close();
        }
    } catch (IOException ex) {
        Logger.getLogger(Server.class.getName()).log(Level.SEVERE, null, ex);
    }
}

public static void main(String args[]) {
    while (true) {
        try {
            Socket socket = new Socket("localhost", 3000);
            String message;
            socket.setSoTimeout(250);
            ObjectOutputStream objectOutputStream = new ObjectOutputStream(socket.getOutputStream());
            objectOutputStream.writeObject("Ping");
            System.out.println("client sent ping");
            try (ObjectInputStream objectInputStream = new ObjectInputStream(socket.getInputStream())) {
                message = (String) objectInputStream.readObject();
                System.out.println("client read: " + message);
            }
            objectOutputStream.close();
            socket.close();
        } catch (IOException | ClassNotFoundException ex) {
            Logger.getLogger(Client.class.getName()).log(Level.SEVERE, null, ex);
        }
        try {
            Thread.sleep(10000);
        } catch (InterruptedException ex) {
            Logger.getLogger(Client.class.getName()).log(Level.SEVERE, null, ex);
        }
    }
}

---

您没有任何东西可以限制发件人的速度。乍一看，我想说，您发送请求的速度比处理请求的速度快，这简直让服务器应接不暇。您在套接字上侦听的“服务器”无法与非限制的“客户端”竞争。

您对服务器和客户端如何使用套接字感到困惑。你可能会在stackoverflow上找到很多例子，甚至可以通过Google找到更多的例子，但一般的习惯用法是：

server:
    create server socket
    call accept on server socket
    with accepted socket
        read request from socket
        write response to socket
        close accepted socket
        loop back to accept

client:
    create socket
    call connect on socket
    write request to socket
    read response from socket
    close socket

（Java会自动为您执行其中一些操作，例如，在创建套接字并指定主机和端口时，套接字类会为您调用connect。）

在您的服务器中，您在读取请求后关闭接受的套接字，然后创建并连接到新的套接字以发送响应，该响应将发送到localhost:3000（您的服务器）上侦听的任何对象。此外，在客户机中，您正在编写请求，但没有读取响应，而且是在一个紧密的循环中进行的，因此您正在创建大量到服务器的连接，这将快速填充accept积压

实际上，生产应用程序会在服务器中使用线程，甚至使用更高级别的库，甚至像Tomcat这样的整个服务器，但在底层，它们基本上都在做上述工作，所以理解这一点很好

为了演示，您的代码应该是这样的：

Server.java

public static void main(String args[]) {
        try {
            ServerSocket serverSocket = new ServerSocket(3000);
            while (true) {
                Socket socket = serverSocket.accept();
                String message = null;
                try {
                    socket.setSoTimeout(3000);
                    try (ObjectInputStream objectInputStream = new ObjectInputStream(socket.getInputStream())) {
                        message = (String) objectInputStream.readObject();
                        System.out.println("Server received " + message);
                    }
                    socket.close();
                } catch (IOException | ClassNotFoundException ex) {
                    //This exception is thrown because it hangs, but why does it hang?
                    Logger.getLogger(Server.class.getName()).log(Level.SEVERE, null, ex);
                }
                if ((message != null) && (message.equals("Ping"))) {
                    try {
                        Socket pongSocket = new Socket("localhost", 3000);
                        pongSocket.setSoTimeout(3000);
                        try (ObjectOutputStream objectOutputStream = new ObjectOutputStream(pongSocket.getOutputStream())) {
                            objectOutputStream.writeObject("Pong");
                            objectOutputStream.flush();
                            System.out.println("Server sent Pong");
                        }
                        pongSocket.close();
                        continue;
                    } catch (IOException ex) {
                        Logger.getLogger(Server.class.getName()).log(Level.SEVERE, null, ex);
                    }
                }
            }
        } catch (IOException ex) {
            Logger.getLogger(Server.class.getName()).log(Level.SEVERE, null, ex);
        }
    }

public static void main(String args[]) {
        while (true) {
            try {
                Socket pingSocket = new Socket("localhost", 3000);
                pingSocket.setSoTimeout(3000);
                try (ObjectOutputStream objectOutputStream = new ObjectOutputStream(pingSocket.getOutputStream())) {
                    objectOutputStream.writeObject("Ping");
                    System.out.println("Client sent Ping");
                    objectOutputStream.flush();
                }
                pingSocket.close();
            } catch (IOException ex) {
                Logger.getLogger(Client.class.getName()).log(Level.SEVERE, null, ex);
            }
        }
    }

public static void main(String args[]) {
    try {
        ServerSocket serverSocket = new ServerSocket(3000);
        while (true) {
            Socket socket = serverSocket.accept();
            socket.setSoTimeout(250);
            String message = null;
            ObjectOutputStream objectOutputStream = new ObjectOutputStream(socket.getOutputStream());
            ObjectInputStream objectInputStream = new ObjectInputStream(socket.getInputStream());
            try {
                message = (String) objectInputStream.readObject();
                System.out.println("server read: " + message);
            } catch (IOException | ClassNotFoundException ex) {
                Logger.getLogger(Server.class.getName()).log(Level.SEVERE, null, ex);
            }
            if ((message != null) && (message.equals("Ping"))) {
                try {
                    objectOutputStream.writeObject("Pong");
                    System.out.println("server sent pong");
                } catch (IOException ex) {
                    Logger.getLogger(Server.class.getName()).log(Level.SEVERE, null, ex);
                }
            }
            objectInputStream.close();
            objectOutputStream.close();
            socket.close();
        }
    } catch (IOException ex) {
        Logger.getLogger(Server.class.getName()).log(Level.SEVERE, null, ex);
    }
}

public static void main(String args[]) {
    while (true) {
        try {
            Socket socket = new Socket("localhost", 3000);
            String message;
            socket.setSoTimeout(250);
            ObjectOutputStream objectOutputStream = new ObjectOutputStream(socket.getOutputStream());
            objectOutputStream.writeObject("Ping");
            System.out.println("client sent ping");
            try (ObjectInputStream objectInputStream = new ObjectInputStream(socket.getInputStream())) {
                message = (String) objectInputStream.readObject();
                System.out.println("client read: " + message);
            }
            objectOutputStream.close();
            socket.close();
        } catch (IOException | ClassNotFoundException ex) {
            Logger.getLogger(Client.class.getName()).log(Level.SEVERE, null, ex);
        }
        try {
            Thread.sleep(10000);
        } catch (InterruptedException ex) {
            Logger.getLogger(Client.class.getName()).log(Level.SEVERE, null, ex);
        }
    }
}

Client.java

public static void main(String args[]) {
        try {
            ServerSocket serverSocket = new ServerSocket(3000);
            while (true) {
                Socket socket = serverSocket.accept();
                String message = null;
                try {
                    socket.setSoTimeout(3000);
                    try (ObjectInputStream objectInputStream = new ObjectInputStream(socket.getInputStream())) {
                        message = (String) objectInputStream.readObject();
                        System.out.println("Server received " + message);
                    }
                    socket.close();
                } catch (IOException | ClassNotFoundException ex) {
                    //This exception is thrown because it hangs, but why does it hang?
                    Logger.getLogger(Server.class.getName()).log(Level.SEVERE, null, ex);
                }
                if ((message != null) && (message.equals("Ping"))) {
                    try {
                        Socket pongSocket = new Socket("localhost", 3000);
                        pongSocket.setSoTimeout(3000);
                        try (ObjectOutputStream objectOutputStream = new ObjectOutputStream(pongSocket.getOutputStream())) {
                            objectOutputStream.writeObject("Pong");
                            objectOutputStream.flush();
                            System.out.println("Server sent Pong");
                        }
                        pongSocket.close();
                        continue;
                    } catch (IOException ex) {
                        Logger.getLogger(Server.class.getName()).log(Level.SEVERE, null, ex);
                    }
                }
            }
        } catch (IOException ex) {
            Logger.getLogger(Server.class.getName()).log(Level.SEVERE, null, ex);
        }
    }

public static void main(String args[]) {
        while (true) {
            try {
                Socket pingSocket = new Socket("localhost", 3000);
                pingSocket.setSoTimeout(3000);
                try (ObjectOutputStream objectOutputStream = new ObjectOutputStream(pingSocket.getOutputStream())) {
                    objectOutputStream.writeObject("Ping");
                    System.out.println("Client sent Ping");
                    objectOutputStream.flush();
                }
                pingSocket.close();
            } catch (IOException ex) {
                Logger.getLogger(Client.class.getName()).log(Level.SEVERE, null, ex);
            }
        }
    }

public static void main(String args[]) {
    try {
        ServerSocket serverSocket = new ServerSocket(3000);
        while (true) {
            Socket socket = serverSocket.accept();
            socket.setSoTimeout(250);
            String message = null;
            ObjectOutputStream objectOutputStream = new ObjectOutputStream(socket.getOutputStream());
            ObjectInputStream objectInputStream = new ObjectInputStream(socket.getInputStream());
            try {
                message = (String) objectInputStream.readObject();
                System.out.println("server read: " + message);
            } catch (IOException | ClassNotFoundException ex) {
                Logger.getLogger(Server.class.getName()).log(Level.SEVERE, null, ex);
            }
            if ((message != null) && (message.equals("Ping"))) {
                try {
                    objectOutputStream.writeObject("Pong");
                    System.out.println("server sent pong");
                } catch (IOException ex) {
                    Logger.getLogger(Server.class.getName()).log(Level.SEVERE, null, ex);
                }
            }
            objectInputStream.close();
            objectOutputStream.close();
            socket.close();
        }
    } catch (IOException ex) {
        Logger.getLogger(Server.class.getName()).log(Level.SEVERE, null, ex);
    }
}

public static void main(String args[]) {
    while (true) {
        try {
            Socket socket = new Socket("localhost", 3000);
            String message;
            socket.setSoTimeout(250);
            ObjectOutputStream objectOutputStream = new ObjectOutputStream(socket.getOutputStream());
            objectOutputStream.writeObject("Ping");
            System.out.println("client sent ping");
            try (ObjectInputStream objectInputStream = new ObjectInputStream(socket.getInputStream())) {
                message = (String) objectInputStream.readObject();
                System.out.println("client read: " + message);
            }
            objectOutputStream.close();
            socket.close();
        } catch (IOException | ClassNotFoundException ex) {
            Logger.getLogger(Client.class.getName()).log(Level.SEVERE, null, ex);
        }
        try {
            Thread.sleep(10000);
        } catch (InterruptedException ex) {
            Logger.getLogger(Client.class.getName()).log(Level.SEVERE, null, ex);
        }
    }
}

---

除了flush（）和swift部分，请看以下问题：。我更喜欢在serverSocket.accept（）调用创建新套接字后创建一个线程来处理IO。创建一个线程并传递客户端套接字，然后在那里执行IO。那么解决方案是什么呢？它不仅仅是一个简单的修复程序，您需要修改代码以使其像上面那样工作。例如，在Server.java中，读取请求后，不要立即关闭套接字，然后打开一个新的套接字。相反，请检查请求，然后发送相应的响应，然后关闭套接字并循环回accept。@ravindra感谢您做了我用“您可能会找到一堆示例”进行的研究我确实在这里搜索过，但我在搜索中指定了Java，您所指的答案是关于Swift的一个问题，尽管答案是一个很好的一般性答案，所以值得一看。