JAVA 是什么导致网络套接字上的流结束？

Question

根据我的理解，end of stream 的全部意义在于告诉输入流何时停止读取数据，这在文件流中是有意义的，但是当它是一个 ObjectInputStream 为什么我要如果我将来可能会发送另一个对象，它会停止读取对象。

在我的例子中，ObjectInputStream 每当它决定有什么东西导致流结束时抛出一个 EOFException。

代码段：

发送中：

public synchronized void sendCommand(CommandBase command){
    try {
        commandOutputStream.writeUnshared(command);
        commandOutputStream.flush();
        System.out.println("Sent " + command.getAction().toString());
    } catch (IOException e) {
        System.out.println("Failed to send " + command.getAction().toString());
        try {
            commandOutputStream.close();
            running = false;
            this.dispose();
            System.out.println("Closing command output stream");
        } catch (IOException e1) {
            e1.printStackTrace();
        }
        e.printStackTrace();
    }
}

接收

while(going && tcpSender.running){
        //Get action from stream
        try {
            System.out.println("Available bytes: " + commandInputStream.available());
            Object command = ((CommandBase) commandInputStream.readObject());
            System.out.println("Action received");

            if (command instanceof CommandBase) {
                if(((CommandBase)command).getAction().equals(ActionType.MouseAction)){
                    System.out.println("Mouse action");
                    //JOptionPane.showMessageDialog(null, "Received Mouse Action");
                    ((MouseCommand)command).doAction(operator);
                }else if(((CommandBase)command).getAction().equals(ActionType.KeyboardAction)){
                    System.out.println("Keyboard action");
                    //JOptionPane.showMessageDialog(null, "Received Keyboard Action: " + ((KeyboardCommand)command).toString());
                    ((KeyboardCommand)command).doAction(operator);
                }else if(((CommandBase)command).getAction().equals(ActionType.CheckBooleanAction)){
                    System.out.println("Check boolean action");
                    udpSender.notifyThis((CheckBooleanCommand)command);
                }else{
                    //JOptionPane.showMessageDialog(null, "Received unknown command " + ((CommandBase)command).getAction().toString());
                    System.out.println("Action type is: " + ((CommandBase)command).getAction().toString());                         
                }
            }
        } catch (EOFException e) {
            System.out.println("EOF-Exception - end of stream reached");
            e.printStackTrace();
            continue;
        } catch(IOException e){
            System.out.println("IO-Exception - Unable to read action \n Closing socket");
            try {
                commandInputStream.close();
                System.out.println("Closed command input stream");
            } catch (IOException e1) {
                e1.printStackTrace();
            }
            e.printStackTrace();
            going = false;
            tcpSender.running = false;
        } catch (ClassNotFoundException e) {
            System.out.println("Class not found - failed to cast to Action");
            e.printStackTrace();
        } 

    }

TL;DR：ObjectInputStream 如何确定它是流的结尾，是什么原因造成的？我该如何解决这个问题？

错误信息：

`

java.io.EOFException at java.io.ObjectInputStream$BlockDataInputStream.peekByte(Unknown Source)

at java.io.ObjectInputStream.readObject0(Unknown Source)

at java.io.ObjectInputStream.readObject(Unknown Source)

Answer 1

How does the ObjectInputStream decide that it's the end of a stream

当 ObjectInputStream 尝试从底层流中读取时会发生这种情况，并且该流 returns -1 ... 这意味着已经到达流的结尾。

and what causes it?

在这种情况下，最可能的解释是远程端（发送方）关闭了它的套接字，或者它已经崩溃......这将导致套接字关闭。

（理论上是有可能断线的，但这种情况只有在比较隐蔽的情况下才会发生，所以忽略掉吧。）

And how can I solve this problem?

你需要明白为什么发送端关闭了socket。不幸的是，我们无法说明原因，因为您提供的代码不是 MCVE。

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