"java.io.StreamCorruptedException: invalid type code: AC"- Error found while running the client code from the server-client java program

Question

Well, I am trying to read a .xml file from the XMLParser so basically I want to read the XML files and print it out from the server to the client, but while running the client code i am getting:

java.io.StreamCorruptedException: invalid type code: AC

The Client code is:

import java.awt.BorderLayout;
import java.awt.Container;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.net.InetAddress;
import java.net.Socket;
import java.net.UnknownHostException;
import java.util.List;

import javax.swing.JComboBox;
import javax.swing.JFrame;

import server.Video;
import server.VideoFile;

@SuppressWarnings("serial")
public class Client extends JFrame{
    Container contentPane;
    @SuppressWarnings("rawtypes")
    JComboBox selectionBox;

    List<Video> video;
    List<VideoFile> videoFile;

    Socket serverSocket;
    String host = "127.0.0.1";
    int port = 1176;
    ObjectInputStream inputFromServer;
    ObjectOutputStream out;

    public Client() throws Exception {
        // line 41 below
            setupGUI();

        System.out.println("Reading the XML File");
        MyXMLReader reader = new MyXMLReader();
        //video = reader.getList("videoList.xml");
        System.out.println("Finished reading");
    }

    public void openSocket() throws UnknownHostException, IOException {
         /** Obtain an address object of the server */
        serverSocket = new Socket("localhost", port);
        System.out.println("Connected to localhost in port: " + port);
        out = new ObjectOutputStream(serverSocket.getOutputStream());
        //out.flush();
        inputFromServer = new ObjectInputStream(serverSocket.getInputStream());

    }

    @SuppressWarnings("unchecked")
    public void getListFromSocket() throws IOException, ClassNotFoundException {
        try{
        video = (List<Video>)inputFromServer.readObject();
        } catch (IOException e) {
            e.printStackTrace();
            System.exit(-1);
        }
        //serverSocket.close();
    }
    public void runClient() throws Exception {

            try {
                openSocket();
                getListFromSocket();
                serverSocket.close();
                setupGUI();
                } catch (UnknownHostException e) {
                System.out.println("Don't know about host : " + host);
                System.exit(-1);
                } catch (IOException e) {
                e.printStackTrace();
                System.out.println("Couldn't open I/O connection : " + host + ":" + port);
                System.exit(-1);
                } catch (ClassNotFoundException e) {
                System.out.println("Class definition not found for incoming object.");
                e.printStackTrace();
                System.exit(-1);
            }

    }

    @SuppressWarnings({ "unchecked", "rawtypes" })
    private void setupGUI() throws Exception{
        setTitle("A Client");
        setSize(600, 400);
        setVisible(true);
        contentPane = getContentPane();
        contentPane.setLayout(new BorderLayout());

            runClient();

        // line 105 below
        String [] selectionListData = new String[video.size()];
        for (int i = 0; i < video.size(); i++) {
        selectionListData[i] = video.get(i).getFilename();
        selectionListData[i] = video.get(i).getID();
        selectionListData[i] = video.get(i).getTitle();
        System.out.println(selectionListData);
        }
        selectionBox = new JComboBox(selectionListData);
        selectionBox.setSelectedIndex(0);
        add(selectionBox, BorderLayout.NORTH);
        selectionBox.addActionListener((ActionListener) this);

        validate();
    }

    public void actionPerformed(ActionEvent e) {
        @SuppressWarnings("rawtypes")
        JComboBox comboBox = (JComboBox)e.getSource();
        String selectedTitle = (String)comboBox.getSelectedItem();
        System.out.println("Selected title : " + selectedTitle);
        }


    public static void main(String[] args) throws IOException, Exception {
            // line 127 below
        new Client();

    }

}

The full error is:

    Connected to localhost in port: 1176
    java.io.StreamCorruptedException: invalid type code: AC
    at java.io.ObjectInputStream.readObject0(Unknown Source)
    at java.io.ObjectInputStream.readObject(Unknown Source)
    at client.Client.getListFromSocket(Client.java:61)
    at client.Client.runClient(Client.java:72)
    at client.Client.<init>(Client.java:40)
    at client.Client.main(Client.java:124)

Can anyone give a fix to this, I am sure its something small but I can't figure it out though.

Thanks

EDIT: The server code is:

package server;

import java.io.IOException;
import java.io.ObjectOutputStream;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.List;
import java.lang.*;

@SuppressWarnings("unused")
public class Server extends Thread implements Runnable{
    List<Video> video;
    static String TimeStamp;
    //Socket Declerations
    ServerSocket serverSocket;
    int port = 1176;
    //String host = "localhost";
    Socket clientSocket;
    ObjectOutputStream outputToClient;



    public Server() {
        Thread();
        System.out.println("Reading the XML File");
        MyXMLReader reader = new MyXMLReader();
        //video = reader.getList("videoList.xml");
        System.out.println("Finished reading");
    }

    public void openSockets() throws IOException {
        try {
            serverSocket = new ServerSocket(port);
            System.out.println("Socket Connection Established....");
        } catch (IOException e) {
            System.out.println("Could not listen on port : " + port);
            System.exit(-1);
        }
        TimeStamp = new java.util.Date().toString();
        System.out.println("Opened socket on : " + port + ", waiting for client. " + TimeStamp);

        try {
            clientSocket = serverSocket.accept();
            //System.out.println("Sending to Client.....");
            } catch (IOException e) {
            System.out.println("Could not accept client.");
            System.exit(-1);
            }
            outputToClient = new ObjectOutputStream(clientSocket.getOutputStream());
    }
    public void writeToSocket() throws IOException {
        outputToClient = new ObjectOutputStream(clientSocket.getOutputStream());
        outputToClient.writeObject(video);
        System.out.println(outputToClient);
    }

    public void Thread() {
        Thread socketThread;
        socketThread = new Thread("Socket") {
        public void run() {
            try {
                openSockets();
                writeToSocket();
                clientSocket.close();
                serverSocket.close();
            } catch (IOException e) {
                System.out.println("Error on sockets connection.");
                e.printStackTrace();
            }
        }
};
socketThread.start();
}

    public static void main(String[] args) throws IOException {
        new Server();
        //new Thread();


    }

}

EDIT: New error after deleting the duplicate entry:

Exception in thread "main" java.lang.NullPointerException
    at client.Client.setupGUI(Client.java:105)
    at client.Client.<init>(Client.java:41)
    at client.Client.main(Client.java:127)

Solution 1

You are double opening an ObjectOutputStream on the same socket in the Server class which is causing special headers to be sent twice.

1: openSockets last line outputToClient = new ObjectOutputStream(clientSocket.getOutputStream());

2: writeToSocket first line outputToClient = new ObjectOutputStream(clientSocket.getOutputStream());

Remove whichever one you want and it should work just fine.

As for the nullpointer you are now receiving I have a feeling that video is null in the client. In the code you have posted that would make sense because in the server you never create a video array and as such the client is just receiving null.

Solution 2

This error is caused by using more than one ObjectOutputStream on the same socket. Use the same ObjectOutputstream and ObjectInputStream for the life of the socket, at both ends. Same goes for most other stream and reader/writer types, except that the consequences of not doing so are usually even more mysterious.

Comments

[Krrose27]

The issue may actually be in the Server. Can you post its code?

[Atif S.]

I have just added the server code above.

[Krrose27]

In client can you add a comment on line 105, 41, and 127? When I toss it in something that has line numbers nothing is matching up with what could be causing a nullpointer.

[Atif S.]

I have just edited the client code and added comments for lines 105,41,127.

[Krrose27]

please see my updated answer.

[Atif S.]

I understand that but the point of this one is that while creating a server-client app, the client should be able to select videos so technically the videoList.xml should not be in the client package so as to test if the server is sending the contents of the video to the client to view it, so if i am getting a null pointer which means that the server is not really sending the video in a serialized manner. I also implemented "Serializable" in the Video class but it didn't help much.

[Krrose27]

SO is yelling at me for so many comments. It says we need to move to a chat but you dont have enough rep. So this will be my last reply. MyXMLReader reader = new MyXMLReader(); //video = reader.getList("videoList.xml"); You have video commented out. Maybe that shouldnt be. IDK. But you need to populate the List<Video> in the Server before sending it to the client.

[Atif S.]

Oh! Thanks for pointing it out. There is a new issue/error. While running the client the following a new error is seen. I have added in the question above. I think its not able to read the file but when I am running the XML Parser in the Client code, the XML Parse runs but in "String [] selectionListData = new String[video.size()];" its not able to get its size

[user207421]

@AtifS. So you are deferencing a null reference variable at MEMEClient.java line 105. As you haven't posted that code it is impossible for anyone to help you further. You should be able to sort out an NPE by yourself but if not you would need to post it and the code concerned as a new question.

[user207421]

He can't 'remove whichever one you want'. He must remove the one in the writeToSocket() method, and store the other one in a member variable. Otherwise he will still get a new OOS per write, and still have the same problem.

[Atif S.]

Thanks, I have removed that. It was not supposed to be there I was experimenting, the first error was caused by the duplicate entry pointed out by @Krroae27. Can you see the edited question for the null pointer error and see any obvious errors I made in the code?

[Krrose27]

@EJP actually the way he has it written it doesn't matter. He closes it after one call. So unless if he is planning to run it differently then what he has he can remove either one.

[Atif S.]

@EJP- It is the same code, I pasted the wrong filename before which might have caused confusion. Its the Client.java code as before

[user207421]

@AtifS. You still haven't told us which is line 105, but, as I said, you are really expected to sort out NullPointerExceptions on your own. Everything you need to do so is in the stack trace. Doing it this way via a forum is just wasting time.

[user207421]

No. Professional programmers are expected to be able to sort out NPEs by themselves. If you had asked that as a question it woudl have been closed as a duplicate almost instantaneously.