Sending objects over sockets - issues i am having

Question

Hi, this is my first time posting on these forums and I have exhausted my mental capacity on this problem i have been having the past few days. Hopefully somone could help me out.
I am doing a uni project, and the goal i am currently trying to achieve is to send an object (serialized) from a client to a server. I will atach the code i have written and i will explain more from there.
This is the server (part of the class, which calls this method)
Constructor:
  public Broker(String bID) throws Exception {
    brokerID = bID;
    bServer = new ServerSocket(Integer.parseInt(bID));
    System.out.println("Broker listening on port " + bID);
    this.start();
Main method
  public static void main(String[] args) throws Exception {
    new Broker("8008");
run method
  public void run() {
    while(true) {
      try {
        Socket bSocket = bServer.accept();
        System.out.println("Accepted a connection from: " + bSocket.getInetAddress());
        brokerServer(bSocket);
        bSocket.close();
        System.out.println("Connection closed");
      catch (Exception e) { e.printStackTrace(); }
Broker Server
  public void brokerServer(Socket bSocket) {
    BufferedReader in = null;
    ObjectOutputStream oos = null;
    PrintWriter out = null;
    ObjectInputStream ois = null;
    try {
      while (true) {
        oos = new ObjectOutputStream(new DataOutputStream(bSocket.getOutputStream()));
        out = new PrintWriter(new OutputStreamWriter(bSocket.getOutputStream()));
        ois = new ObjectInputStream(bSocket.getInputStream());
        in = new BufferedReader(new InputStreamReader(bSocket.getInputStream()));
        out.println("Connection with Broker on port " + brokerID + " established");
        out.flush();
        //read in first line
        String str = in.readLine();
        //if lineis null, break while loop
        if (str == null)  break;
        else {
          //a request is recieved from user to get user certificate
          if (str.trim().equals("GETUSERCERT")) {
            //read in the userName, size of paywords and user publick key (used in certificate)
            String userName = in.readLine();
            String size = in.readLine();
            PublicKey userPk = (PublicKey) ois.readObject();
            //generate user certificate
            UserCertificate uc = generateUserCertificate(userName, userPk, Integer.parseInt(size, 10));
            //send text to user stating next message is user certififcate
            out.println("SENDUSERCERT");
            out.flush();
            //user Certificate
            oos.writeObject( (UserCertificate) uc);
            oos.flush();
            break;
          if (str.trim().equals("FINISH"))
            break;
        ois.close();
        oos.close();
        out.close();
        in.close();
    catch(Exception e) { e.printStackTrace(); }
This is the client
  private void requestUserCertificate(int sizeOfPaywordChain, String BrokerID) {
    String host = "localhost";
    ObjectOutputStream oos = null;
    ObjectInputStream ois = null;
    PrintWriter out = null;
    BufferedReader in = null;
    Socket u2bSocket = null;
    try {
      u2bSocket = new Socket(host, Integer.parseInt(BrokerID));
      System.out.println("Connecting to Broker on port " + BrokerID);
      ois = new ObjectInputStream(new DataInputStream(u2bSocket.getInputStream()));
      oos = new ObjectOutputStream(u2bSocket.getOutputStream());
      out = new PrintWriter(new OutputStreamWriter(u2bSocket.getOutputStream()));
      in = new BufferedReader(new InputStreamReader(u2bSocket.getInputStream()));
      //Informs broker that a user certificate is being requested
      out.println("GETUSERCERT");
      //send to broker, username and size of payword chain
      out.println(userName);
      out.println(sizeOfPaywordChain);
      out.flush();
      //send user's public key accross
      oos.writeObject((PublicKey) userPublicKey);
      oos.flush();
      out.println("FINISH");
      out.flush();
      //wait for response
      while(true) {
        //read in line
        String str = in.readLine();
        //if line is null, break while loop
        if (str == null) break;
        //if line read is "SENDUSERCERT" then next line is userCertificate sent from Broker
        if (str.trim().equals("SENDUSERCERT")) {
          //read User Certificate
          userCert = (UserCertificate)ois.readObject();
          break;
        else System.out.println(str);
      //close connections and streams
      u2bSocket.close();
      ois.close();
      oos.close();
      out.close();
      in.close();
    catch (Exception e) { e.printStackTrace(); }
  }I will be regurarly checking this thread, so any other code which you think i should post i will, i can post is ASAP.
The problem
First time i run the programs, it works perfectly, however when i run the client program again, it shows this error
java.io.EOFException
     at java.io.ObjectInputStream$BlockDataInputStream.peekByte(ObjectInputStream.java:2438)
     at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1245)
     at java.io.ObjectInputStream.readObject(ObjectInputStream.java:324)
     at User.requestUserCertificate(User.java:75)
     at User.main(User.java:278)the broker server doesn't display anything.
Would anyone have any idea whats going on??
Sometimes when i run it, it might display the above error, or it might work. its about 50/50. I have read heaps of similar problems people have had and posted on this forum, but i still don't have any luck in solving this delema.
Any kind of help will be greatly appreciated.
Rish

Answer 1

I see one problem with the code. You are opening both ObjectInputStream ois and a BufferedReader in on the same socket. This won't work as "in" will read ahead to fill up its buffer. This could cause "ois" to find the socket already at end of stream prematurely. I would only use the Object Streams and send the strings as objects.