How to transfer objects between Android and PC using Bluetooth and ObjectOutputStream and ObjectInputStream?

Question

I have met a problem when implementing communication between PC and android using BT. I have an application which works correctly on WIFI communication, using standard java Socket, and its streams. I am trying to add Bt communication. Android side code for opening streams uses standard BluetoothSocket (communication is established, and it's ok):

mOos = new ObjectOutputStream(btSocket.getOutputStream());
mOos.flush();
mOis = new ObjectInputStream(btSocket.getInputStream());

On PC side I use Bluecove 2.1.

mOos = new ObjectOutputStream(mStreamConn.openOutputStream());
mOos .flush();
mOis = new ObjectInputStream(mStreamConn.openInputStream());

Streams are initialized properly. I am sending initial message from android to PC

protected synchronized void sendAwaitingMsg() throws IOException {
    Message msg;
    while((msg = mOutgoingMsgQueue.poll()) != null) {
        mOos.writeObject(msg);
    }
    mOos.flush();
}

And then try to read it on PC side

protected void getIncomingMsg() throws IOException, ClassNotFoundException {
    if(mOis.available() > 0) {
        Message msg = (Message)mOis.readObject();

        if(msg.mControlHeader > 0) {
            mKeepRunning = false;
        } else {
            msg.setHandlerId(mId);
            mConnectionManager.acceptNewMessage(msg);
        }
    }
}

But mOis.available() is always 0 which means that it does not receive send message. My Message object class:

public class Message extends LinkedHashMap implements Serializable, Comparable {
static final long serialVersionUID = 10275539472837495L;

protected long mHandlerId;
protected int mType;
protected int mPriority;
public int mControlHeader = 0;



public int getType() {
    return mType;
}

public void setType(int type) {
    this.mType = type;
}

public long getHandlerId() {
    return mHandlerId;
}

public void setHandlerId(long handlerId) {
    this.mHandlerId = handlerId;
}

public int getPriority() {
    return mPriority;
}

public void setPriority(int priority) {
    mPriority = priority;
}

@Override
public int compareTo(Object o) {
    return mPriority - ((Message)o).mPriority;
}

}

The same operations, on standard java socket, and network communication works like a charm. Where is the problem?

Answer 1

I had similar troubles with bluetooh communication between android and PC. I finally found some info about bluecove (implementation of bluetooth libraries in java) and a great commented example here in the following link:

http://fivedots.coe.psu.ac.th/~ad/jg/blue4/blueCoveEcho.pdf

Here there's another example but without using bluecove:

http://fivedots.coe.psu.ac.th/~ad/jg/blue1/blueEcho.pdf

I hope it helps you.