使用TCP over socket从服务器端向客户端发送ArrayList

Question

我试图将一个对象从服务器端发送到客户端，但找不到问题。以下是我在客户端遇到的错误：

java.io.StreamCorruptedException: invalid type code: 43
at java.io.ObjectInputStream.readObject0(Unknown Source)
at java.io.ObjectInputStream.readObject(Unknown Source)
at connection.MainClient.doAll(MainClient.java:56)
at connection.TestScreen$2.actionPerformed(TestScreen.java:82)
at javax.swing.AbstractButton.fireActionPerformed(Unknown Source)
at javax.swing.AbstractButton$Handler.actionPerformed(Unknown Source)
at javax.swing.DefaultButtonModel.fireActionPerformed(Unknown Source)
at javax.swing.DefaultButtonModel.setPressed(Unknown Source)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(Unknown Source)
at java.awt.Component.processMouseEvent(Unknown Source)
at javax.swing.JComponent.processMouseEvent(Unknown Source)
at java.awt.Component.processEvent(Unknown Source)
at java.awt.Container.processEvent(Unknown Source)
at java.awt.Component.dispatchEventImpl(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.LightweightDispatcher.retargetMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.processMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.dispatchEvent(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Window.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
at java.awt.EventQueue.access$200(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue$4.run(Unknown Source)
at java.awt.EventQueue$4.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)

下面是服务器端方法：无限循环中的separate方法只是从文件中读取，并将用户名和密码解析为ArrayList，这是服务器类中的实例变量。

    public void doStuff() throws Exception
{
    ServerSocket serverSocket = new ServerSocket(5001);
    Socket clientSocket = serverSocket.accept();
    PrintWriter out = new PrintWriter(clientSocket.getOutputStream(), true);
    BufferedReader in = new BufferedReader(
            new InputStreamReader(
            clientSocket.getInputStream()));
    ObjectOutputStream objectOutput = new ObjectOutputStream(clientSocket.getOutputStream());
    String inputLine;
    out.println("Connected");
    while(true)
    {
        seperate();
        while ((inputLine = in.readLine()) != null) 
        {
            if(inputLine.equalsIgnoreCase("users"))
                objectOutput.writeObject(getUserNames());
            else
                if(inputLine.equalsIgnoreCase("pass"))
                    objectOutput.writeObject(getPassWords());
                else
                    if(inputLine.equalsIgnoreCase("stop"))
                        objectOutput.reset();
        }
    }
}

以下是从服务器请求信息的客户端：

public boolean doAll(String name, String pass) throws Exception
{
    try 
    {
        kkSocket = new Socket("PC", 5001);
        out = new PrintWriter(kkSocket.getOutputStream(), true);
        in = new BufferedReader(new InputStreamReader(kkSocket.getInputStream()));
    } 
    catch (UnknownHostException e) 
    {
        System.err.println("Don't know about host: PC.");
        System.exit(1);
    }
    catch (IOException e) 
    {
        System.err.println("Couldn't get I/O for the connection to: PC.");
        System.exit(1);
    }

    ObjectInputStream objectInput = new ObjectInputStream(kkSocket.getInputStream());

    out.println("user");
    Object obj = objectInput.readObject();
    users = (ArrayList<String>)obj;
    out.println("pass");
    obj = objectInput.readObject();
    this.pass = (ArrayList<String>)obj;
    out.println("stop");
    objectInput.close();
    out.close();
    in.close();
    kkSocket.close();

    if(userIsRegistered(name,pass))
        return true;
    return false;
}

我对学习服务器套接字和套接字还不熟悉，但我在这里试图实现的是以下目标。当我在另一节课上按下按钮时，我会这样做：

MainClient b = new MainClient();
login = b.doAll(userField.getText(),passField.getText());
Login is obviously a boolean.

几乎是一个通过服务器到cleint的登录系统，当按下登录按钮时，它会调用一个客户端连接到该服务器，获取用户列表，并在服务器上传递，该服务器存储在指定目录中的文本文件中。然后，当客户端接收到这些信息时，它会从我从两个文本字段中获取的字符串中检查它是否可能是用户，并返回true或false。然后关闭服务器的套接字，每次都应该重新连接，对吗？

我的主要问题是如何修复它不断抛出的错误？

Answer 1

不能对字节输入流使用InputStreamReader。它需要输入流中的字符/字符串。请尝试ObjectInputStream。

提示一下：输入流类型应该在服务器端和客户端都匹配。你不能把它们混在一起。在服务器上使用的是ObjectOutputStream，因此相应的ObjectInputStream应该在客户端上使用。

Answer 2

您的代码流程如下所示：

1. 服务器已启动，正在等待与客户端的连接
2. 服务器使用serverSocket从客户端接受连接。accept（）
3. 服务器通过out使用PrintWriter对象向客户端发送String消息（“已连接”）。println（“已连接”）
4. 客户端正在使用ObjectInputStream对象读取该消息，这导致流不匹配，因此违反了内部一致性检查。这就是为什么在客户端抛出StreamCorruptedException。因此，与其使用ObjectInputStream读取服务器发送的普通消息，不如使用上面创建的BufferedReader对象

因此，在客户端，您的代码应该修改为：

ObjectInputStream objectInput = new ObjectInputStream(kkSocket.getInputStream());
String message = in.readLine();//use BufferedReader to read the plain message coming from Server.
System.out.println("Message from server: "+message);
out.println("user");
Object obj = objectInput.readObject();