Cross-platform object sharing

Question

Hi,
I am developing a file sharing client-server project.
Server is a distributed server in which users are created. Clients used to connect to the server using that user name.
For the first time when the client logged in to the server, a directory is created for that user in his name and set it as the user's home directory for that user.
After that the user's home directory content is filled up in the JTable and it is sent to the client as TableModel object. In client side that TableModel object will be received and that will be set as the tablemodel for its JTable using the following method
client's JTable object .setModel("received TableModel Object from the server");
This is working fine if the server and client both belong to the same OS.
i.e,
I have tested this with server in windows 98 and client in windows 98. Working fine.
I have tested with server in Redhat Linux 9 and client in Redhat Linux 9. Working fine.
But when I tested with server in Redhat Linux and client in windows, there is an error while reading the TableModel object received from the server.
How can i solve this problem?
Please help me soon.
Eagerly waiting for the reply.
Thank you.

Answer 1

The error is ClassNotFoundException. Or the reading of bytes is incomplete.
I have done with a simple client-server example.
In this when the client connect to the server, the server will send its current working directory's content.
Server :
import java.io.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.table.*;
import java.net.*;
import java.util.*;
class tblobjSendServer implements Runnable
     ServerSocket server;
     Thread t;
     JTable tblList;
     public tblobjSendServer()
          String[] colNames={"","Name","Type","Size","Date","Path"};
          tblList=new JTable(new newTableModel(new Object[0][0],colNames));
          try
               server=new ServerSocket(2000);
               System.out.println("Listening to the port 2000");
          catch(IOException ie)
          t=new Thread(this);
          t.start();
     public void run()
          while (true)
               try
                    Socket theConnection=server.accept();
                    InputStream rawIn=new BufferedInputStream(theConnection.getInputStream());
                    Reader in=new InputStreamReader(new BufferedInputStream(theConnection.getInputStream()),"ASCII");
                    OutputStream out=new BufferedOutputStream(theConnection.getOutputStream());
                    loadTblList();
                    ByteArrayOutputStream bout=new ByteArrayOutputStream();
                    ObjectOutputStream oout=new ObjectOutputStream(bout);
                    oout.writeObject(tblList.getModel());
                    oout.flush();
                    byte[] tblData=bout.toByteArray();
                    oout.close();
                    bout.close();
                    String msgToSend="OK "+tblData.length+"\n";
                    //sending OK msg : "OK <tblData byte array size>"
                    out.write(msgToSend.getBytes("ASCII"));
                    out.flush();
                    //sending the tblData byte array
                    out.write(tblData);
                    out.flush();
               catch(IOException e)
     public void loadTblList()
          File curDir=new File(System.getProperty("user.dir"));
          //---------------------------- Filtering Directories --------------------------------
          FileFilter dirFilter=new FileFilter()
               public boolean accept(File file)
                    return file.isDirectory();
          File[] dirlist=curDir.listFiles(dirFilter);
          //---------------------------- Filtering Directories end--------------------------          
          //------------ Filtering files ---------------------------------------------------
          FileFilter fileFilter=new FileFilter()
               public boolean accept(File file)
                    return !file.isDirectory();
          File[] filelist=curDir.listFiles(fileFilter);
          //------------ Filtering files end -----------------------------------------------
          ((DefaultTableModel)tblList.getModel()).setNumRows(0);
          if (dirlist.length>0)
               Arrays.sort(dirlist); //sorting dirlist
               String folderImg="";
               String name="";
               String type="DIR";
               String size="";
               String lastModiDate="";
               String fullPath="";
               long longdate;
               Date modiDate;
               Calendar cal;
               for(int i=0;i<dirlist.length;i++)
                    name=dirlist.getName();
                    //------ Calculating Date and Time ------------
                    longdate=dirlist[i].lastModified();
                    modiDate=new Date(longdate);
                    cal=new GregorianCalendar();
                    cal.setTime(modiDate);
                    lastModiDate=cal.get(Calendar.DATE)+"/"+(cal.get(Calendar.MONTH)+1)
                              +"/"+cal.get(Calendar.YEAR);          
                    lastModiDate+=" "+cal.get(Calendar.HOUR)+":"+cal.get(Calendar.MINUTE)+":"
                              +cal.get(Calendar.SECOND);
                    if(cal.get(Calendar.AM_PM)==0)
                         lastModiDate+="AM";
                    else if(cal.get(Calendar.AM_PM)==1)
                         lastModiDate+="PM";     
                    //------- Calculation completed ---------------
                    try
                         fullPath=dirlist[i].getCanonicalPath();
                    catch(IOException e)
                    ((DefaultTableModel)tblList.getModel()).addRow(new Object[]
                    {folderImg,name,type,size,lastModiDate,fullPath
          if (filelist.length>0)
               Arrays.sort(filelist); //sorting filelist
               String fileImg="";
               String name="";
               String type="FILE";
               String size="";
               String lastModiDate="";
               String fullPath="";
               long longdate;
               Date modiDate;
               Calendar cal;
               for(int i=0;i<filelist.length;i++)
                    name=filelist[i].getName();
                    //------ Calculating Date and Time ------------
                    longdate=filelist[i].lastModified();
                    modiDate=new Date(longdate);
                    cal=new GregorianCalendar();
                    cal.setTime(modiDate);
                    lastModiDate=cal.get(Calendar.DATE)+"/"+(cal.get(Calendar.MONTH)+1)
                              +"/"+cal.get(Calendar.YEAR);          
                    lastModiDate+=" "+cal.get(Calendar.HOUR)+":"+cal.get(Calendar.MINUTE)+":"
                              +cal.get(Calendar.SECOND);
                    if(cal.get(Calendar.AM_PM)==0)
                         lastModiDate+="AM";
                    else if(cal.get(Calendar.AM_PM)==1)
                         lastModiDate+="PM";     
                    //------- Calculation completed ---------------
                    //size=(filelist[i].length()/1024f)+" KB";
                    size=filelist[i].length()+" bytes";
                    try
                         fullPath=filelist[i].getCanonicalPath();
                    catch(IOException e)
                    ((DefaultTableModel)tblList.getModel()).addRow(new Object[]
                    {fileImg,name,type,size,lastModiDate,fullPath
     }//end loadTblLocal()
     public static void main(String args[])
          new tblobjSendServer();
class newTableModel extends DefaultTableModel implements Serializable
     public newTableModel(Object[][] data,Object[] columns)
          super(data,columns);
     public boolean isCellEditable(int row,int col)
          return false;
     public Class getColumnClass(int column)
          Vector v=(Vector) dataVector.elementAt(0);
          return v.elementAt(column).getClass();
//end class newTableModel
Client :
import java.io.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.table.*;
import java.net.*;
import java.util.*;
class tblobjReceiveClient extends JFrame implements ActionListener
     JTable tblList;
     JButton btnGet;
     public tblobjReceiveClient()
          super("Receive TableModel object from the server");
          //tblList=new JTable(new Object[0][0],colData);
          String[] colNames={"","Name","Type","Size","Date","Path"};
          tblList=new JTable(new newTableModel(new Object[0][0],colNames));
          btnGet=new JButton("Get TableModel");
          btnGet.addActionListener(this);
          Container cpane=getContentPane();
          cpane.add(new JScrollPane(tblList,ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS,ScrollPaneConstants.HORIZONTAL_SCROLLBAR_ALWAYS),BorderLayout.CENTER);
          cpane.add(btnGet,BorderLayout.SOUTH);
          setDefaultCloseOperation(EXIT_ON_CLOSE);
          setSize(400,300);
          setVisible(true);
     public void actionPerformed(ActionEvent ae)
          if (ae.getSource()==btnGet)
               try
                    Socket theConnection=new Socket("localhost",2000);
                    InputStream rawIn=new BufferedInputStream(theConnection.getInputStream());
                    Reader in=new InputStreamReader(new BufferedInputStream(theConnection.getInputStream()),"ASCII");
                    OutputStream out=new BufferedOutputStream(theConnection.getOutputStream());
                    StringBuffer strbuf=new StringBuffer();
                    int c;
                    while (true)
                         c=in.read();
                         if(c=='\n')
                              break;
                         strbuf.append((char)c);     
                    String msg=strbuf.toString();
                    StringTokenizer st=new StringTokenizer(msg);
                    if (st.hasMoreTokens())
                         String okToken=st.nextToken();
                         if (okToken.equals("OK"))
                              if (st.hasMoreTokens())
                                   String sizeToken=st.nextToken();
                                   int size=0;
                                   try
                                        size=Integer.parseInt(sizeToken);
                                   catch(NumberFormatException nfe)
                                   ByteArrayOutputStream bout=new ByteArrayOutputStream();
                                   c=0;
                                   for(int i=0;i<size;i++)
                                        c=rawIn.read();
                                        bout.write(c);
                                   byte[] tblData=bout.toByteArray();
                                   ObjectInputStream oin=new ObjectInputStream(new ByteArrayInputStream(tblData));
                                   TableModel tblobj=null;
                                   try
                                        tblobj=(TableModel) oin.readObject();
                                   catch(ClassNotFoundException cnfe)
                                        System.out.println("Error occurred while reading the object");
                                   if(tblobj!=null)
                                        tblList.setModel(tblobj);
               catch(IOException ie)
     public static void main(String args[])
          new tblobjReceiveClient();
class newTableModel extends DefaultTableModel implements Serializable
     public newTableModel(Object[][] data,Object[] columns)
          super(data,columns);
     public boolean isCellEditable(int row,int col)
          return false;
     public Class getColumnClass(int column)
          Vector v=(Vector) dataVector.elementAt(0);
          return v.elementAt(column).getClass();
//end class newTableModelNote : I have tested with another simple client-server example which will create and send a simple Student object. It is working fine with different platform.
class Student implements Serializable
     String name,age,city;
     public Student(String name,String age,String city)
          this.name=name;
          this.age=age;
          this.city=city;
     public String toString()
          return "Name : "+name+"\nAge : "+age+"\nCity : "+city;
}Thank You.