Exception when readObj() - please give me a hand!

Question

I am writing a Client/Server application where Server simply sends object to the client. The first object goes well but when the client side reads the second object, the exception caught was "Type code out of range, is -84". Can anybody kindly give me a hand? Thanks very much in advance!
Result on Client:
C:\thesisTest>java TestCli
@Line 1: Get ready!!!
Type code out of range, is -84
receive error.
Source for Server :
import java.net.*;
import java.io.*;
import java.util.*;
import sendNode;
public class TestSer {
     static sendNode sendNodeObj = new sendNode();
static String inputLine;
     public static void main(String[] args) throws IOException {
ServerSocket serverSocket = null;
try {
serverSocket = new ServerSocket(4444);
} catch (IOException e) {
System.err.println("Could not listen on port: 4444.");
System.exit(1);
Socket clientSocket = null;
try {
clientSocket = serverSocket.accept();
} catch (IOException e) {
System.err.println("Accept failed.");
System.exit(1);
OutputStream o = clientSocket.getOutputStream();
ObjectOutput out=new ObjectOutputStream(o);
BufferedReader in = new BufferedReader(
                    new InputStreamReader(
                    clientSocket.getInputStream()));
sendNodeObj.sendMsg="@Line 1: Get ready!!!";
sendNodeObj.typeNode=-1;
out.writeObject(sendNodeObj);
out.flush();
out=new ObjectOutputStream(o);
sendNodeObj.sendMsg="@Line 2: Please input Start";
sendNodeObj.typeNode=-1;
out.writeObject(sendNodeObj);
out.flush();
inputLine = in.readLine();
while (!inputLine.equalsIgnoreCase("Start")) {
     sendNodeObj.sendMsg="@Error, Please input Start";
sendNodeObj.typeNode=-1;
out.writeObject(sendNodeObj);
out.flush();
inputLine = in.readLine();
out.close();
in.close();
clientSocket.close();
serverSocket.close();
Source for Client:
import java.io.*;
import java.net.*;
import java.util.*;
import java.applet.Applet;
import sendNode;
public class TestCli extends Applet {
static sendNode recNodeObj=null;
public static void main(String[] args) throws IOException {
BufferedReader stdIn = new BufferedReader(new InputStreamReader(System.in));
Socket kkSocket = null;
PrintWriter out = null;
try {
kkSocket = new Socket("127.0.0.1", 4444);
out = new PrintWriter(kkSocket.getOutputStream(), true);
} catch (UnknownHostException e) {
System.err.println("Don't know about host.");
System.exit(1);
} catch (IOException e) {
System.err.println("Couldn't get I/O for the connection to: taranis.");
System.exit(1);
InputStream i= kkSocket.getInputStream();
ObjectInput in= new ObjectInputStream(i);
try {
     recNodeObj = (sendNode)in.readObject();
System.out.println(recNodeObj.sendMsg);
     recNodeObj = (sendNode)in.readObject();
System.out.println(recNodeObj.sendMsg);
if (recNodeObj.sendMsg.equalsIgnoreCase("@Line 2: Please input Start")) {
out.println("Start");
} catch (Exception e) {
System.out.println(e.getMessage());
System.out.println("receive error.");
System.exit(1);
out.close();
in.close();
stdIn.close();
kkSocket.close();

Answer 1

You are not being consistent in the way you use ObjectOutputStream and ObjectInputStream.
For every new ObjectOutputStream you create you need a corresponding new ObjectInputStream, because ObjectOutputStream writes a header that ObjectInputStream reads.
In general, you probably don't want to use multiple OutputOutputStream objects on a given underlying socket, because it is ineffecient in the way class names etc are encoded.
Sylvia.