multi client chat server throwing exceptions and not allowing connections after disconnect

Question

It's hard to fit it in the title but every time a client disconnects, a lot of exceptions are thrown and the server does not allow any more connections after the DC. Here is the error i get:

java.net.SocketException: Socket closed
at java.net.SocketInputStream.read(Unknown Source)
at java.net.SocketInputStream.read(Unknown Source)
at java.io.ObjectInputStream$PeekInputStream.read(Unknown Source)
at java.io.ObjectInputStream$PeekInputStream.readFully(Unknown Source)
at java.io.ObjectInputStream$BlockDataInputStream.readShort(Unknown Source)
at java.io.ObjectInputStream.readStreamHeader(Unknown Source)
at java.io.ObjectInputStream.<init>(Unknown Source)
at ClientHandler.setupStreams(ClientHandler.java:34)
at ClientHandler.run(ClientHandler.java:22)

Now i expect to get this exception because yea... The client closed the connection between the server and the client. but what i can't understand is why the client wont allow connections after the first disconnect. I am assuming that it breaks out of the while loop but why? Here is the code that takes the clients connection, accepts it and hands it off to the handler class:

public class ClientConnector
{
public static JTextField userText;
public static JTextArea chatWindow;
public static int Connections = 0;
public static Vector sendQueue = new Vector();
public static ArrayList<ObjectOutputStream> Streams = new ArrayList<ObjectOutputStream>();
public static Scanner input = new Scanner(System.in);


public ClientConnector()
{

}

public static void runServer()
{
    try
    {   
        System.out.println("[Info] Attempting to bind to port 1337.");
        @SuppressWarnings("resource")
        ServerSocket serversocket = new ServerSocket(1337);
        System.out.println("[Info] Bound to port 1337.");
        System.out.println("[Info] Waiting for client connections...");
        while(true)
        {
            Socket socket = serversocket.accept();
            new ClientHandler(socket).start();
            Connections += 1;


        }
    }
    catch (IOException e)
    {
        e.printStackTrace();
    }
}
}

That's fairly simple. Now for the code that handles the clients connection:

public class ClientHandler extends Thread
{
Socket ConnectedClient;
static ObjectOutputStream Output;
static ObjectInputStream Input;
public static boolean isError = false;
public static int updateCounter = 0;

ClientHandler(Socket socket)
{
    ConnectedClient = socket;
}

public void run()
{

    while(true)
    {
        setupStreams();//22
        WhileChatting();
    }
}

public void setupStreams()
{
    try 
    {
        if(isError == false)
        {
            Output = new ObjectOutputStream(ConnectedClient.getOutputStream());
            Input = new ObjectInputStream(ConnectedClient.getInputStream());//34
            ClientConnector.Streams.add(Output);
        }   
    }
    catch (IOException e)
    {
        isError = true;
        e.printStackTrace();
    }

}


public static void WhileChatting()
{
    String Message = "";
    do
    {
        try
        {
            if(isError == false)
            {
                Message = (String)Input.readObject();
                for(int i = 0; i < ClientConnector.Streams.size(); i++)
                {
                    ClientConnector.Streams.get(i).writeObject(Message);
                    System.out.println(Message);
                }
            }

        }
        catch(ClassNotFoundException CNFE)
        {
            isError = true;
            CNFE.printStackTrace();
        }
        catch(EOFException eof)
        {
            for(int i = 0; i < ClientConnector.Streams.size(); i++)
            {
                try
                {
                    Output.close();
                    Input.close();
                    ClientConnector.Streams.get(i).close();
                    ClientConnector.Streams.remove(i);
                    System.out.println("Connection lost");
                }
                catch (IOException e)
                {
                    e.printStackTrace();
                }

            }
        }
        catch (IOException e)
        {
            isError = true;
            e.printStackTrace();
        }

    }
    while(Message != "/disconnect");
}

public static void sendMessage(String message)
{
    try
    {
        if(isError == false)
        {
            Output.writeObject(message);
            System.out.println(message);
        }
    }
    catch(IOException Ex)
    {
        isError = true;
        Ex.printStackTrace();
    }
}

public static void sendServerMessage(String message)
{
    int Limit = 0;
    try
    {
        for(int i = 0; i < ClientConnector.Streams.size(); i++)
        {
            if(Limit == 0)
            {
                ClientConnector.Streams.get(i).writeObject("\247c[Server] \247d" + message);
                System.out.println("\247c[Server] \247d" + message);
                Limit = 1;
            }
        }
    }
    catch (IOException e)
    {
        e.printStackTrace();
    }
}

public static void closeConnections()
{
    try
    {
        if(isError == false)
        {
            Output.close();
            Input.close();
            //ConnectedClient.close();
        }
    }
    catch(IOException Ex)
    {
        isError = true;
        Ex.printStackTrace();
    }
}

}

I have commented in the affected lines. The error happens after the client disconnects. I don't know if it's the exception causing the while loop to break or weather it's something else. How can i make this code continute to allow incoming connectinos after the client disconnects. I have tried debugging and using System.out.println. Thanks in advance to all who answered.

score 0 · Answer 1 · answered Apr 23 '13 at 00:01

Now i expect to get this exception because yea... The client closed the connection between the server and the client.

No. This exception means that you closed the Socket and then tried to do further I/O on it. Nothing to do with the peer.

but what i can't understand is why the client wont allow connections after the first disconnect.

There are numerous problems with your code.

You must use the same ObjectInputStream and ObjectOutputStream for the life of the Socket, at both ends. At present you are creating a new pair, and adding them to the data structure, every time around the loop.
When you catch EOFException on one Socket, you are closing all the sockets. You should only close one, the one you got the exception from, and then you must break out of all loops and allow the thread to exit.
You should basically change your while loop from while (true) to while (!isError) and stop testing isError everywhere else. I would get rid of the whileChatting method and incorporate it into this while loop. And you don't need the inner do loop. You only need one loop that reads until EOS or a disconnect command.

multi client chat server throwing exceptions and not allowing connections after disconnect

1 Answers1