Question

I’m trying to manage a connection between my phone and another bluetooth device. I’m doing all this using java Android. This is the code I used for connecting the socket using my device:

First I find the Bluetooth device and I create the socket:

BluetoothDevice btNonin = null;
for (BluetoothDevice device : pairedDevices)
{
        if (device.getName().contains("Nonin")) 
        {           
            // We found the device      
            exito = true;
            try
            {
                // We create the socket
                Method m = device.getClass().getMethod("createRfcommSocket", new Class[] {int.class});
                socket = (BluetoothSocket) m.invoke(device, 1);
                socket.connect();
            }
            catch (Exception e)
            {
                Dialogs.showInfoDialog(NONIN_OFF, this);
            }
       }
}

Afther that I create the data bytes I want the remote bluetooth to receive using some code to convert ASCII to byte:

String[] parts = mensaje.split(" ");
String res = "";
if(parts != null && parts.length > 0)
{
    for (String s : parts)
    {
        if (s.length() != 2)
           break;
            byte izq, der;
        izq = (byte)char2ascii(s.charAt(0));
        der = (byte)char2ascii(s.charAt(1));
        byte aux2 = (byte)((izq << 4) + der);
        res += (char)aux2;
    }
}

And then I send the data to the bluetooth device:

// We send the data bytes
DataOutputStream dOut = new DataOutputStream(socket.getOutputStream());
dOut.writeBytes(res);
dOut.flush();

Until here it works fine. It sends the data bytes to my device. But then I want to wait for any response from my device, and then I try this:

//Waiting for response
DataInputStream dIn = new DataInputStream(socket.getInputStream());
try
{
    byte response = '\u0000';
    while (dIn.readByte() == '\u0000')
    {
        response = dIn.readByte();
    }
    Dialogs.showInfoDialog("Response: " + response, this);
}
catch (Exception e)
{
    Dialogs.showInfoDialog("No se ha recibido respuesta: " + e.toString(), this);
}

But then, on the line where I make dIn.readByte it shows the message Error:

java.io.IOException: Connection reset by peer

And I don’t know why the connection is reset or what happens, as I can debug the line:

DataInputStream dIn = new DataInputStream(socket.getInputStream());

With no mistakes, so I guess the socket is still opened… What is happening here?

Thank you so much for your help!

Answer 1

There are several causes of this problem. The typical cause is that you have written to a connection which has already been closed by the peer. In other words, an application protocol error.

Also your exception handling needs work. If you get any IOException on a socket other than a timeout you must close it, it is dead.