Java SwingWorker and TCP connections not working properly

Question

I have the following code, which describes that if a window opens, it should render a dialog visible, connect to the server, and receive data:

private void formWindowOpened(java.awt.event.WindowEvent evt) {                                  
    this.jDialog1.setVisible(true);
    con = new Conexion();
    SwingWorker work = new SwingWorker() {
        @Override
        public Object doInBackground() {
            con.recibirDatos();
            return null;
        }

        @Override
        public void done() {
            jDialog1.dispose();
            jDialog2.setVisible(true);
        }
    };
    work.execute();
}

Now, Conexion does the following, client-wise:

public Conexion() {
    try
    {
        this.puerto = 7896;
        this.s = new Socket("localhost", puerto);
        this.entrada = new DataInputStream(s.getInputStream());
        this.salida = new DataOutputStream(s.getOutputStream());
    }
    catch(UnknownHostException e){ System.out.println("Socket: "+e.getMessage()); }
    catch(EOFException e){ System.out.println("EOF: "+e.getMessage()); }
    catch(IOException e){ System.out.println("IO: "+e.getMessage()); }
}

public void recibirDatos() {
    try
    {
        this.salida.writeUTF("sendData");
        System.out.println("Leyendo...");
        this.color = this.entrada.readUTF();
        this.ancho = this.entrada.readInt();
        System.out.println("Datos recibidos: "+color+" "+ancho);
    }
    catch(UnknownHostException e){ System.out.println("Socket: "+e.getMessage()); }
    catch(EOFException e){ System.out.println("EOF: "+e.getMessage()); }
    catch(IOException e){ System.out.println("IO: "+e.getMessage()); }
}

Server-wise, the following happens when a connection is read:

public void enviarDatos(String color, int anchoLinea) {
    try
    {
        System.out.println(entradaCliente.readUTF()+"! Enviando datos: "+color+" "+anchoLinea);
        salidaCliente.flush();
        salidaCliente.writeUTF(color);
        salidaCliente.writeInt(anchoLinea);
        System.out.println("Datos enviados.");
    }
    catch(EOFException e){ System.out.println("EOF: "+e.getMessage()); }
    catch(IOException e){ System.out.println("IO: "+e.getMessage()); }
}

The issue:

When I execute this, the client gets stuck on readUTF() although the server already sent the data.
If I only send and receive an integer, I get the value -1393754107 instead of the number I'm sending, however the client doesn't get stuck.
When I send data from the client to the server it works just fine.

What could be the problem? Thank you beforehand.

EDIT: I also found out that, if the server shuts down while the client is waiting due to readUTF(), the client gets an IOException, which means the client is actually connected to the server, but for some reason it's not reading data from it!

You might compare your code to this complete, working [example](http://stackoverflow.com/a/3245805/230513). — trashgod, Dec 14 '12 at 21:09
What gets my attention is the usage of `Scanner` and `PrintWriter` instead of `DataInputStream` and `DataOutputStream`. Why should I choose one over the other? — Carlos Vergara, Dec 14 '12 at 23:06
Oh, and also, I just tested using `Scanner` and `PrintWriter` and I got the same result while trying to read a String. For some reason the client is not receiving any data from the server!! — Carlos Vergara, Dec 15 '12 at 00:01
See also this [Q&A](http://stackoverflow.com/q/4009157/230513). — trashgod, Dec 15 '12 at 02:32
Thank you!! That gave me an idea I'm going to post and it worked!! — Carlos Vergara, Dec 15 '12 at 02:37

score 0 · Accepted Answer · answered Dec 15 '12 at 02:38

0

To make this work, all I did was to replace the usual DataInputStream and DataOutputStream with ObjectInputStream and ObjectOutputStream. And issue solved, it worked.

answered Dec 15 '12 at 02:38

Carlos Vergara

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Java SwingWorker and TCP connections not working properly

1 Answers1