Question

I’m trying to communicate with a bluetooth device. The information I have on the device states that

“The communications protocol is ASCII, commas separate output values. The message is terminated by carriage return and line feed pair. When saved as a file using a terminal emulator these results can be read into an Excel spreadsheet.”

How do I send and receive from this device? I have tried using InputStreamReader and OutputStreamWriter, but I don’t think that’s working.

EDIT:

for sending data I’m trying:

public void send(String s){
            try {
                writer.write(s);
            } catch (IOException e) {
                e.printStackTrace();
            }
        }

where

try {
                tmpIn = socket.getInputStream();
                tmpOut = socket.getOutputStream();
            } catch (IOException e) { }

            inStream = tmpIn;
            writer = new OutputStreamWriter(tmpOut);

You can also see there where I am using inStream that is a simple InputStream. I have also tried InputStreamReader, but I just got random characters back. With the InputStream I am only reading 4 bytes no matter what I send the device, so I’m not sure if even the sending is working.

What should I be using? Thanks!

Answer 1

I am following up on this in case anyone else is having the same problems. One of the problems I was having was that the device I was trying to communicate with was expecting a specific order of /n and /r and would lock up if that was incorrect so I had no was of knowing if it was working or not.

Here is he code I use for sending and receiving, I have used it on a couple of devices now and it seems to work well.

    /**
 * This thread runs during a connection with a remote device.
 * It handles all incoming and outgoing transmissions.
 */
private class ConnectedThread extends Thread {
    private final BluetoothSocket socket;
    private final InputStream inStream;
    private final OutputStream outStream;
    private final DataInputStream datIn;

    public ConnectedThread(BluetoothSocket socket) {
        Log.d(TAG, "create ConnectedThread");
        this.socket = socket;
        InputStream tmpIn = null;
        OutputStream tmpOut = null;

        // Get the BluetoothSocket input and output streams
        try {
            tmpIn = socket.getInputStream();
            tmpOut = socket.getOutputStream();
        } catch (IOException e) {
            Log.e(TAG, "temp sockets not created", e);
        }

        inStream = tmpIn;
        outStream = tmpOut;
        datIn = new DataInputStream(inStream);
    }

    public void run() {
        Log.i(TAG, "BEGIN ConnectedThread");
        Bundle data = new Bundle();

        // Keep listening to the InputStream while connected
        while (true) {
            Log.i(TAG, "Reading...");
            try {
                // Read from the InputStream
                String results;
                Log.i(TAG, "Recieved:");
                results = datIn.readLine();
                Log.i(TAG, results);

             // Send the obtained bytes to the UI Activity
                data.putString("results", results);
                Message m = handler.obtainMessage(); // get a new message from the handler
                m.setData(data); // add the data to the message
                m.what = MESSAGE_READ;
                handler.sendMessage(m);
            } catch (IOException e) {
                Log.e(TAG, "disconnected", e);
                handler.obtainMessage(MESSAGE_DISCONNECTED).sendToTarget();
                setState(STATE_NONE);
                // Start the service over to restart listening mode
                break;
            }
        }
    }

    /**
     * Write to the connected OutStream.
     * @param buffer  The bytes to write
     */
    public void write(byte[] buffer) {
        try {
            outStream.write(buffer);
            Log.i(TAG, "Sending: " + new String(buffer));

        } catch (IOException e) {
            Log.e(TAG, "Exception during write", e);
        }
    }

    public void cancel() {
        try {
            socket.close();
        } catch (IOException e) {
            Log.e(TAG, "close() of connect socket failed", e);
        }
    }
}

/**
 * Write to the ConnectedThread in an unsynchronized manner
 * @param out The bytes to write
 * @see ConnectedThread#write(byte[])
 */
public void send(byte[] out) {
    // Create temporary object
    ConnectedThread r;
    // Synchronize a copy of the ConnectedThread
    synchronized (this) {
        if (state != STATE_CONNECTED) return;
        r = connectedThread;
    }
    // Perform the write unsynchronized
    r.write(out);
}