java.net.SocketException: Socket is closed TCP Connection

Question

Doing some debugging, I think the error occurs in this method below. The method basically sends an ID (string) to the server and the server after receiving this ID looks up a record which it sends back to the client. The IDs are displayed in a GUI JList which the user selects so each time the user clicks on a different ID in the JList, this method is activated by the ListSelectionListener event. Once the client receives the record from the server, it displays it in a JTextField. Everything works as expected when user first clicks an ID in JList. But when you click another record in the list, I get the exception:

java.net.SocketException: Socket is closed

Edit: Now I'm getting:

java.net.SocketException: Software caused connection abort: recv failed

Client program:

    import java.awt.BorderLayout;
import java.awt.Dimension;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.net.Socket;
import java.net.UnknownHostException;
import java.util.ArrayList;

import javax.swing.DefaultListModel;
import javax.swing.JFrame;
import javax.swing.JList;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextField;
import javax.swing.event.ListSelectionEvent;
import javax.swing.event.ListSelectionListener;


public class ClientGUI extends JFrame implements ListSelectionListener{

    //gui components
    JList jlist = null;
    String requestID = null; //Assigned to selected ID in JList. 
    JScrollPane scpane = null;
    JTextField field = null;
    JPanel pane = null;
    DefaultListModel<String> listModel = null;
    ArrayList<String> idList = null;

    //client stuff:
    Socket sock1 = null;
    Socket sock2 = null;
    ObjectInputStream in = null;
    ObjectOutputStream out = null;

    public ClientGUI() throws ClassNotFoundException{
        //get List of IDs from Server1
        try{
            sock1 = new Socket("FahadAhmed-PC", 8889); 
            in = new ObjectInputStream(sock1.getInputStream());
            idList = new ArrayList<String>(29);
            ArrayList<Customer> custList = null;
            custList = (ArrayList<Customer>) in.readObject();
            for(Customer c : custList){
                idList.add(c.getID());
            }

            in.close();
            sock1.close();

            sock2 = new Socket("FahadAhmed-PC", 8888); 
            ArrayList streams = new ArrayList(3); 
            streams.add(out = new ObjectOutputStream(sock2.getOutputStream()));
            streams.add(in = new ObjectInputStream(sock2.getInputStream()));

        }catch(UnknownHostException e) {
            System.err.println("Don't know about host: FahadAhmed-PC");
            System.exit(1);
        }catch(IOException e){
            System.err.println(e);
            System.exit(1);
        }

        //Setup GUI
        jlist = new JList(idList.toArray());
        jlist.setVisibleRowCount(10);
        scpane = new JScrollPane(jlist);
        jlist.addListSelectionListener(this);
        pane = new JPanel(new BorderLayout());
        pane.setPreferredSize(new Dimension(300, 300));
        field = new JTextField(29);
        field.setEditable(false);
        pane.add(scpane, BorderLayout.PAGE_START);
        pane.add(field, BorderLayout.PAGE_END);

        this.setContentPane(pane);
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        this.pack();
        this.setVisible(true);
    }

    public static void main(String args[]) throws ClassNotFoundException{
        ClientGUI gui = new ClientGUI();
    }


    @Override
    public void valueChanged(ListSelectionEvent arg0) {
        if(!arg0.getValueIsAdjusting())
            try {
                System.out.println(jlist.getSelectedValue().toString());
                getRecord(jlist.getSelectedValue().toString());
            } catch (ClassNotFoundException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }       
    }

    private void getRecord(String getID) throws ClassNotFoundException {
        try{

            //System.out.println(getID + "sent to getRecord method");
            out.writeObject(getID);

            String rec = (String) in.readObject();

            field.setText(rec);
            //in.close();
            //sock2.shutdownInput();
            out.flush();
            //sock2.shutdownOutput();
            //out.close();

        }catch(UnknownHostException e) {
            System.err.println("Don't know about host: FahadAhmed-PC");
            System.exit(1);
        }catch(IOException e){
            System.err.println(e);
            System.exit(1);
        }
    }


}

Answer 1

Closing either the input stream or the output stream closes the socket, and I don't know why you are closing anything here, but there is another problem here. You must use the same ObjectInputStream and ObjectOutputStream for the life of the socket, at both ends. Otherwise the two peers will get out of sync and you will start to see things like StreamCorruptedException: invalid type code.

Answer 2

Closing the input/output stream closes the socket. You need to use the shutdownInput method on socket, to close just the input stream:

//do sth with fromSocket ... and close it 
socket.shutdownInput();
socket.shutdownOutput();