Develop Reference

Bluetooth connection problems

I have a client on a PC and a server on a tablet. I know the MAC addresses for both which means I do not do discoveries.
1. On the client if I use
connectString = "btspp://" + MACaddress + ":4;authenticate=false;encrypt=false;master=false";
It connects fine.
If I change the CN number (4) to anything else, it does not work. How is this number determined?
2. Everything works fine if the tablet is a Samsung with Android 5.0.2 When I use a Qunyico tablet with Android 10, it does not work. I get an error: Failed to connect; [10051] A socket operation was attempted to an unreachable network. What is the problem?
Client on PC – code taken from “Bluetooth-java-client-master”
public class IrcBluetoothClient {
private static void openConnection(String MACaddress) throws IOException {
// Tries to open the connection.
String connectString = "btspp://" + MACaddress + ":4;authenticate=false;encrypt=false;master=false";
StreamConnection connection = (StreamConnection) Connector.open(connectString);
if (connection == null) {
System.err.println("Could not open connection to address: " + MACaddress);
System.exit(1);
}
// Initializes the streams.
OutputStream output = connection.openOutputStream();
InputStreamReader isr = new InputStreamReader(System.in);
BufferedReader reader = new BufferedReader(isr);
// Starts the listening service for incoming messages.
ExecutorService service = Executors.newSingleThreadExecutor();
service.submit(new IncomingMessagesLoggingRunnable(connection));
// Main loop of the program which is not complete yet
LocalDevice localDevice = LocalDevice.getLocalDevice();
while (true) {
String toSend = reader.readLine();
byte[] toSendBytes = toSend.getBytes(StandardCharsets.US_ASCII);
output.write(toSendBytes);
System.out.println("[" + localDevice.getFriendlyName() + " - " +
localDevice.getBluetoothAddress() + "]: " + toSend);
System.exit(1);
}
Server on tablet – code taken from https://developer.android.com/guide/topics/connectivity/bluetooth
private static final UUID A_UUID = UUID.fromString("00001101-0000-1000-8000-00805F9B34FB");
public BTacceptConnections( BluetoothAdapter mBluetoothAdapter) {
// Use a temporary object that is later assigned to mmServerSocket
// because mmServerSocket is final.
BluetoothServerSocket tmp = null;
try {
// A_UUID is the app's UUID string, also used by the client code.
tmp = mBluetoothAdapter.listenUsingRfcommWithServiceRecord(NAME, A_UUID);
} catch (IOException e) {
Log.e(TAG, "Socket's listen() method failed", e);
}
mmServerSocket = tmp;
// Closes the connect socket and causes the thread to finish.
public void cancel(){
try {
mmServerSocket.close();
}catch (IOException e){
}
runFlag = 1;
}
//***********************************************************************************************
//
// This thread runs all the time listening for incoming connections.
//
public void run() {
BluetoothSocket socket = null;
// Keep listening until exception occurs or a socket is returned.
while (runFlag == 0) {
try {
socket = mmServerSocket.accept();
} catch (IOException e) {
Log.e(TAG, "Socket's accept() method failed", e);
break;
}
if (socket != null) { // If a connection was accepted
// A connection was accepted. Perform work associated with
// the connection in a separate thread.
// manageMyConnectedSocket(socket);
}else{
try {
mmServerSocket.close();
} catch (IOException e) {
e.printStackTrace();
}
break;
}
}

I know the MAC addresses for both which means I do not do discoveries.
Official Linux Bluetooth protocol stack BlueZ uses D-BUS API to establish bluetooth communication. If you check adapter-api, scanning will create device objects that you need to establish a communication which means discovering is not only done to retrieve MAC addresses only.
Your case might be the same, I would suggest doing discovery first.

Packet Sent but cannot Received Packets

I've been editing androids toyvpn sample project for vpn and i got this one for my sample app
I know there is something wrong/missing with my code because when i manually set up the vpn via android settings, there are packets Receive that's why
i've been searching how to receive packets and i dont know how to get this working.
here is my source code that VCL that extends VpnService
import android.app.PendingIntent;
import android.net.VpnService;
import android.os.ParcelFileDescriptor;
import android.util.Log;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.DatagramChannel;
/**
* Created by Jameshwart Lopez on 8/18/15.
*/
public class VCL extends VpnService {
private static final String TAG = "VpnClientLibrary";
private Thread mThread;
private ParcelFileDescriptor mInterface;
private String mServerAddress;
private String mServerPort;
private PendingIntent mConfigureIntent;
private String mParameters;
//a. Configure a builder for the interface.
Builder builder = new Builder();
public void vclRun(){
try {
//a. Configure the TUN and get the interface.
mInterface = builder.setSession("thesessionname")
.addAddress("192.168.0.1",24)
.addDnsServer("8.8.8.8")
.addRoute("0.0.0.0", 0).establish();
//b. Packets to be sent are queued in this input stream.
FileInputStream in = new FileInputStream(mInterface.getFileDescriptor());
//b. Packets received need to be written to this output stream.
FileOutputStream out = new FileOutputStream(mInterface.getFileDescriptor());
// Allocate the buffer for a single packet.
ByteBuffer packet = ByteBuffer.allocate(32767);
//c. The UDP channel can be used to pass/get ip package to/from server
DatagramChannel tunnel = DatagramChannel.open();
// Connect to the server, localhost is used for demonstration only.
mServerAddress="";//some of the vpn ip address here
mServerPort="1723";
InetSocketAddress server = new InetSocketAddress(mServerAddress, Integer.parseInt(mServerPort) );
tunnel.connect(server);
// For simplicity, we use the same thread for both reading and
// writing. Here we put the tunnel into non-blocking mode.
tunnel.configureBlocking(false);
// Authenticate and configure the virtual network interface.
handshake(tunnel);
//d. Protect this socket, so package send by it will not be feedback to the vpn service.
protect(tunnel.socket());
int timer = 0;
//e. Use a loop to pass packets.
while (true) {
//get packet with in
//put packet to tunnel
//get packet form tunnel
//return packet with out
//sleep is a must
// Assume that we did not make any progress in this iteration.
boolean idle = true;
// Read the outgoing packet from the input stream.
int length = in.read(packet.array());
if (length > 0) {
// Write the outgoing packet to the tunnel.
packet.limit(length);
tunnel.write(packet);
packet.clear();
// There might be more outgoing packets.
idle = false;
// If we were receiving, switch to sending.
if (timer < 1) {
timer = 1;
}
}
// Read the incoming packet from the tunnel.
length = tunnel.read(packet);
if (length > 0) {
// Ignore control messages, which start with zero.
if (packet.get(0) != 0) {
// Write the incoming packet to the output stream.
out.write(packet.array(), 0, length);
}
packet.clear();
// There might be more incoming packets.
idle = false;
// If we were sending, switch to receiving.
if (timer > 0) {
timer = 0;
}
}
// If we are idle or waiting for the network, sleep for a
// fraction of time to avoid busy looping.
if (idle) {
Thread.sleep(100);
// Increase the timer. This is inaccurate but good enough,
// since everything is operated in non-blocking mode.
timer += (timer > 0) ? 100 : -100;
// We are receiving for a long time but not sending.
if (timer < -15000) {
// Send empty control messages.
packet.put((byte) 0).limit(1);
for (int i = 0; i < 3; ++i) {
packet.position(0);
tunnel.write(packet);
}
packet.clear();
// Switch to sending.
timer = 1;
}
// We are sending for a long time but not receiving.
//if (timer > 20000) {
// throw new IllegalStateException("Timed out");
//}
}
}
} catch (Exception e) {
// Catch any exception
e.printStackTrace();
} finally {
try {
if (mInterface != null) {
mInterface.close();
mInterface = null;
}
} catch (Exception e) {
}
}
}
private void handshake(DatagramChannel tunnel) throws Exception {
// To build a secured tunnel, we should perform mutual authentication
// and exchange session keys for encryption. To keep things simple in
// this demo, we just send the shared secret in plaintext and wait
// for the server to send the parameters.
// Allocate the buffer for handshaking.
ByteBuffer packet = ByteBuffer.allocate(1024);
// Control messages always start with zero.
String password = "";//vpn password here
packet.put((byte) 0).put(password.getBytes()).flip();
// Send the secret several times in case of packet loss.
for (int i = 0; i < 3; ++i) {
Log.e("packetsdata", packet.toString());
packet.position(0);
tunnel.write(packet);
}
packet.clear();
// Wait for the parameters within a limited time.
for (int i = 0; i < 50; ++i) {
Thread.sleep(100);
// Normally we should not receive random packets.
int length = tunnel.read(packet);
if (length > 0 && packet.get(0) == 0) {
configure(new String(packet.array(), 1, length - 1).trim());
return;
}
}
//throw new IllegalStateException("Timed out");
}
private void configure(String parameters) throws Exception {
// If the old interface has exactly the same parameters, use it!
if (mInterface != null) {
Log.i(TAG, "Using the previous interface");
return;
}
// Configure a builder while parsing the parameters.
Builder builder = new Builder();
for (String parameter : parameters.split(" ")) {
String[] fields = parameter.split(",");
try {
switch (fields[0].charAt(0)) {
case 'm':
builder.setMtu(Short.parseShort(fields[1]));
break;
case 'a':
builder.addAddress(fields[1], Integer.parseInt(fields[2]));
break;
case 'r':
builder.addRoute(fields[1], Integer.parseInt(fields[2]));
break;
case 'd':
builder.addDnsServer(fields[1]);
break;
case 's':
builder.addSearchDomain(fields[1]);
break;
}
} catch (Exception e) {
throw new IllegalArgumentException("Bad parameter: " + parameter);
}
}
// Close the old interface since the parameters have been changed.
try {
mInterface.close();
} catch (Exception e) {
// ignore
}
// Create a new interface using the builder and save the parameters.
mInterface = builder.setSession(mServerAddress)
.setConfigureIntent(mConfigureIntent)
.establish();
mParameters = parameters;
Log.i(TAG, "New interface: " + parameters);
}
}
this is how i use the class above
private Thread mThread;
/*
* Services interface
* */
#Override
public int onStartCommand(Intent intent, int flags, int startId) {
// Start a new session by creating a new thread.
mThread = new Thread(this, "VpnRunnable");
//start the service
mThread.start();
/*
*service is left "started" and will later be restarted by the system
* http://android-developers.blogspot.com.au/2010/02/service-api-changes-starting-with.html
*/
return START_STICKY;
}
#Override
public void onDestroy() {
if (mThread != null) {
mThread.interrupt();
}
super.onDestroy();
}
#Override
public synchronized void run() {
/*
* to run the vpn interface call the vclRun method inside VCL class
* */
this.vclRun();
}

Firstly, check that there are bytes being sent to your android device. As it won't be reading anything if there is nothing to receive.
Then have a look at this, as it may be messing up your connection.
You need to include this in the onStartCommand:
// The handler is only used to show messages.
if (mHandler == null) {
mHandler = new Handler(this);
}
// Stop the previous session by interrupting the thread.
if (mThread != null) {
mThread.interrupt();
}
// Extract information from the intent.
String prefix = getPackageName();
mServerAddress = intent.getStringExtra(prefix + ".ADDRESS");
mServerPort = intent.getStringExtra(prefix + ".PORT");
mSharedSecret = intent.getStringExtra(prefix + ".SECRET").getBytes();
// Start a new session by creating a new thread.
mThread = new Thread(this, "ToyVpnThread");
mThread.start();
return START_STICKY;
And also the details (some shown below) of the sychronized void.
#Override
public synchronized void run() {
try {
Log.i(TAG, "Starting");
// If anything needs to be obtained using the network, get it now.
// This greatly reduces the complexity of seamless handover, which
// tries to recreate the tunnel without shutting down everything.
// In this demo, all we need to know is the server address.
InetSocketAddress server = new InetSocketAddress(
mServerAddress, Integer.parseInt(mServerPort));
// We try to create the tunnel for several times. The better way
// is to work with ConnectivityManager, such as trying only when
// the network is avaiable. Here we just use a counter to keep
// things simple.
for (int attempt = 0; attempt < 10; ++attempt) {
mHandler.sendEmptyMessage(R.string.connecting);
// Reset the counter if we were connected.
// See BELOW
if (run(server)) {
attempt = 0;
}
// Sleep for a while. This also checks if we got interrupted.
Thread.sleep(3000);
} /..../
You are not managing your thread actions well. It is advised to receive any bytes that need to be received before attempting your run. That not doing so can cause problems.
I would go back through your code and put in the things you took out.
I also suggest you change your code here:
packet.put((byte) 0).put(password.getBytes()).flip();
Try to use explicit encoding:
packet.put((byte) 0).put(password.getBytes("UTF-8")).flip();
As data can be lost without it. See this answer:
https://stackoverflow.com/a/7947911/3956566
I have checked and your project is using "UTF-8".
Let me know if this doesn't help.

Why is my android receiver dropping 10-60% of UDP broadcast packets?

I have an 802.3 wired transmitter application on my computer that I've written to broadcast UDP packets every 10ms. Each broadcast packet contains a 4-byte integer value that is unique to its particular packet, which allows me to figure out on the receiver end exactly how many packets have been dropped.
I have verified that the transmitter works with Wireshark. I set up four 802.11 receivers (2 android phones and 2 laptop computers) on the same network. The laptops received 95% of the UDP broadcast packets; one phone received 89%; the other phone received 40%.
Why?
Here is part of my android receiver code:
public class NetThread extends Thread {
int[] pkt_nums;
int p;
NetThread(int[] pkt_nums)
{
this.pkt_nums = pkt_nums;
for (int i=0; i<pkt_nums.length; i++)
{
pkt_nums[i]=0;
}
p = 0;
}
#Override
public void run()
{
receiveData();
}
public void receiveData()
{
// request permission to do network operations in manifest file...done
// start the network side of things
DatagramSocket sock = null;
DatagramPacket pkt = null;
try
{
byte[] data = new byte[C.PAYLOAD_MAX];
sock = new DatagramSocket(C.NET_PORT);
sock.setSoTimeout(C.NET_SO_TIMEOUT);
pkt = new DatagramPacket(data, 0, C.PAYLOAD_MAX);
while (true)
{
Thread.sleep(0); // allow for an interrupt
try
{
sock.receive(pkt);
int length = pkt.getLength();
boolean success = writeToBuffer(pkt.getData(), length);
if (!success) break;
}
catch (InterruptedIOException e)
{
// thrown when a timeout occurs
Log.d(C.DTAG, "net: no packets yet");
}
}
Log.d(C.DTAG, "buffer is full. done receiving.");
if (sock != null) sock.close();
}
catch (InterruptedException x)
{
Log.d(C.DTAG, "net: was interrupted.");
}
catch (SocketException e)
{
Log.d(C.DTAG, "net: SocketException");
e.printStackTrace();
}
catch (IOException e)
{
Log.d(C.DTAG, "net: IOException");
e.printStackTrace();
}
if (sock != null) sock.close();
}
public boolean writeToBuffer(byte[] data, int length)
{
// each packet should have exactly 4 bytes - a number
int pkt_num = data[0] & 0x000000FF | data[1]<<8 & 0x0000FF00 | data[2]<<16 & 0x00FF0000 | data[3]<<24 & 0xFF000000;
if (p < pkt_nums.length)
{
pkt_nums[p++] = pkt_num;
return true; // success
}
else
{
return false;
}
}
}
I declare the above class in my main activity as follows:
mNetThrd = new NetThread(pkt_nums);
mNetThrd.setDaemon(true);
mNetThrd.start();
I will try boosting the thread priority now, but I have a feeling I'm doing something wrong. I need to get at least 95% of UDP broadcast packets for my application.
More details: Laptops and phones are situated next to each other, 30 ft from the router with line-of sight visibility. Laptop 1 received 95% of packets. Laptop 2 received 94%. Phone 1 received 89%. Phone 2 received 40%. Both ran the same app. Other network traffic is minimal. Dropped packets in android typically happen in groups of 20-50 at a time. 802.11 has a clean channel. Each packet contains a 4-byte payload.
Is there something drastically wrong with my receiver code or is this another issue altogether?

Connecting Android device to multiple Bluetooth serial embedded peers

I'm trying to find a solution for this setup:
I have a single Android device, which I would like to connect to multiple serial embedded devices...
And here is the thing, using the "Normal" way to retrieve the Bluetooth socket, doesn't work on all devices, and while it does, I can connect to multiple devices, and send and receive data to and from multiple devices.
public final synchronized void connect()
throws ConnectionException {
if (socket != null)
throw new IllegalStateException("Error socket is not null!!");
connecting = true;
lastException = null;
lastPacket = null;
lastHeartBeatReceivedAt = 0;
log.setLength(0);
try {
socket = fetchBT_Socket_Normal();
connectToSocket(socket);
listenForIncomingSPP_Packets();
connecting = false;
return;
} catch (Exception e) {
socket = null;
logError(e);
}
try {
socket = fetchBT_Socket_Workaround();
connectToSocket(socket);
listenForIncomingSPP_Packets();
connecting = false;
return;
} catch (Exception e) {
socket = null;
logError(e);
}
connecting = false;
if (socket == null)
throw new ConnectionException("Error creating RFcomm socket for" + this);
}
private BluetoothSocket fetchBT_Socket_Normal()
throws Exception {
/* The getType() is a hex 0xXXXX value agreed between peers --- this is the key (in my case) to multiple connections in the "Normal" way */
String uuid = getType() + "1101-0000-1000-8000-00805F9B34FB";
try {
logDebug("Fetching BT RFcomm Socket standard for UUID: " + uuid + "...");
socket = btDevice.createRfcommSocketToServiceRecord(UUID.fromString(uuid));
return socket;
} catch (Exception e) {
logError(e);
throw e;
}
}
private BluetoothSocket fetchBT_Socket_Workaround()
throws Exception {
Method m;
int connectionIndex = 1;
try {
logDebug("Fetching BT RFcomm Socket workaround index " + connectionIndex + "...");
m = btDevice.getClass().getMethod("createRfcommSocket", new Class[]{int.class});
socket = (BluetoothSocket) m.invoke(btDevice, connectionIndex);
return socket;
} catch (Exception e1) {
logError(e1);
throw e1;
}
}
private void connectToSocket(BluetoothSocket socket)
throws ConnectionException {
try {
socket.connect();
} catch (IOException e) {
try {
socket.close();
} catch (IOException e1) {
logError("Error while closing socket", e1);
} finally {
socket = null;
}
throw new ConnectionException("Error connecting to socket with" + this, e);
}
}
And here is the thing, while on phones which the "Normal" way doesn't work, the "Workaround" way provides a solution for a single connection. I've searched far and wide, but came up with zip.
The problem with the workaround is mentioned in the last link, both connection uses the same port, which in my case, causes a block, where both of the embedded devices can actually send data, that is not been processed on the Android, while both embedded devices can receive data sent from the Android.
Did anyone handle this before?
There is a bit more reference here,
UPDATE:
Following this (that I posted earlier) I wanted to give the mPort a chance, and perhaps to see other port indices, and how other devices manage them, and I found out the the fields in the BluetoothSocket object are different while it is the same class FQN in both cases:
Detils from an HTC Vivid 2.3.4, uses the "workaround" Technic:
The Socket class type is: [android.bluetooth.BluetoothSocket]
mSocket BluetoothSocket (id=830008629928)
EADDRINUSE 98
EBADFD 77
MAX_RFCOMM_CHANNEL 30
TAG "BluetoothSocket" (id=830002722432)
TYPE_L2CAP 3
TYPE_RFCOMM 1
TYPE_SCO 2
mAddress "64:9C:8E:DC:56:9A" (id=830008516328)
mAuth true
mClosed false
mClosing AtomicBoolean (id=830007851600)
mDevice BluetoothDevice (id=830007854256)
mEncrypt true
mInputStream BluetoothInputStream (id=830008688856)
mLock ReentrantReadWriteLock (id=830008629992)
mOutputStream BluetoothOutputStream (id=830008430536)
**mPort 1**
mSdp null
mSocketData 3923880
mType 1
Detils from an LG-P925 2.2.2, uses the "normal" Technic:
The Socket class type is: [android.bluetooth.BluetoothSocket]
mSocket BluetoothSocket (id=830105532880)
EADDRINUSE 98
EBADFD 77
MAX_RFCOMM_CHANNEL 30
TAG "BluetoothSocket" (id=830002668088)
TYPE_L2CAP 3
TYPE_RFCOMM 1
TYPE_SCO 2
mAccepted false
mAddress "64:9C:8E:B9:3F:77" (id=830105544600)
mAuth true
mClosed false
mConnected ConditionVariable (id=830105533144)
mDevice BluetoothDevice (id=830105349488)
mEncrypt true
mInputStream BluetoothInputStream (id=830105532952)
mLock ReentrantReadWriteLock (id=830105532984)
mOutputStream BluetoothOutputStream (id=830105532968)
mPortName "" (id=830002606256)
mSocketData 0
mSppPort BluetoothSppPort (id=830105533160)
mType 1
mUuid ParcelUuid (id=830105714176)
Anyone have some insight...

WOW, every time this strike me down with one big WTF?
This was a race condition issue, which clearly works on one version of android, and not on another. On Android peer I was parsing the packets received from the socket:
public class SocketListener
implements Runnable {
private boolean stop;
private OnIncomingPacketListener packetListener;
#Override
public void run() {
InputStream inputStream;
try {
stop = false;
inputStream = socket.getInputStream();
while (!stop) {
Packet packet = Packet.getPacket(inputStream);
lastPacket = packet;
if (packet.getDescriptor() == Packet.HeartBeat)
lastHeartBeatReceivedAt = System.currentTimeMillis();
else if (packet.getDescriptor() == Packet.LogEntry)
log.append(((LogEntryPacket) packet).getLogEntry());
synchronized (this) {
if (packetListener != null)
packetListener.onIncomingData(EmbeddedDevice.this, packet);
}
}
} catch (IOException e) {
logError("----- BLUETOOTH IO ERROR -----\n #: " + EmbeddedDevice.this, e);
return;
} catch (RuntimeException e) {
logError("----- BLUETOOTH LISTENER ERROR -----\n #: " + EmbeddedDevice.this, e);
throw e;
} finally {
socketListeningThread = null;
}
}
}
Where the Packet.getPacket(inputStream) is:
public static synchronized Packet getPacketInstance(InputStream inputStream)
throws IOException {
int data = inputStream.read();
Packet type = null;
for (Packet packetType : values())
if (packetType.packetType == data) {
type = packetType;
break;
} // race condition here...
if (type == null)
throw new IllegalArgumentException("Unknown packet type: " + data);
try {
Packet packet = type.incomingPacketType.newInstance();
packet.setDescriptor(type);
packet.readPacketData(inputStream);
return packet;
} catch (IOException e) {
throw e;
} catch (Exception e) {
throw new IllegalStateException("Error instantiating type: " + type.incomingPacketType.getName(), e);
}
}
And every time a packet is completed, the next thread should have gone in to perform it parsing.
My guess is that there is some sort of lock on the port, that together with my implementation caused the second thread to block indefinitely, once I've removed the parsing to different instances per thread, the issue dissolved.
This insight was inspired by Daniel Knoppel, the guy from the mPort link.
Thanks Daniel!

android bluetooth application unresponsive during phone call

I have an application which communicates with a bluetooth device via async task
if I receive a phone call and during the call I return to the app
the screen dims and the application is unresponsive
back button doesn't work... and no ANR dialog is shown
any ideas?
here is the code which handles the connection:
#Override
protected Object doInBackground(Object... params) {
//boolean protocolUpdated;
int read = 0; // The amount of bytes read from the socket.
byte[] buff = new byte[MessageHandler.BUFFERSIZE]; // The data buffer.
byte[] tmpSend = null; // Misc bytes arrays returned from ProtocolParser as answers to send after decoding calls.
in = null;
out = null;
try {
if (Float.parseFloat(version) > 2.2){
Method m = dev.getClass().getMethod("createRfcommSocket", new Class[] {int.class});
sock = (BluetoothSocket) m.invoke(dev, 1);
}
else sock = dev.createRfcommSocketToServiceRecord(UUID_RFCOMM_GENERIC); // UUID is constant for serial BT devices.
sock.connect(); // connect to the BT device. This is rather heavy, may take 3 secs.
sendMessage(MESSAGE_CONNECTION_ESTABLISHED);
in = sock.getInputStream();
out = sock.getOutputStream();
timer = new Timer();
startFinishTimer(); //initialize finish timer
while(read != -1) { // read = -1 means EOF.
do { // as long as there is anything to send in the send queue - send it.
tmpSend = parser.nextSend();
if(tmpSend != null){
String msg = parseMessage(tmpSend);
Log.d("Writing:",msg);
out.write(tmpSend);
}
} while(tmpSend != null);
read = in.read(buff); // read. This is a blocking call, to break this, interrupt the thread.
timer.cancel();
startFinishTimer(); //read is a blocking call so timer should be restarted only after read bytes.
parser.parse(buff,read); // parse the read message using the logic in the ProtocolParser derived class.
tmpSend = parser.getPool(); // if pool ack is required - send it.
if (tmpSend != null){
Log.d("Writing:",parseMessage(tmpSend));
out.write(tmpSend);
}
if (read != 0){
Log.d("Read:",parseMessage(buff));
tmpSend = parser.getAnswer(); // if answer is required (based on message) - send it.
if(tmpSend != null){
out.write(tmpSend);
}
}
else {
Exception e = new IOException();
throw e;
}
}
}catch (IOException e){
e.printStackTrace();
Log.d("Connection: ", "Bluetooth Connection CRASHED!");
sendMessage(MESSAGE_CONNECTION_LOST);
}catch (Exception e){
e.printStackTrace();
}
return null;
}

Actually there is not enough context to find your problem.
Make sure that you launch this task from Main thread in other case PostExecute will be attached to wrong thread, you could get a race.
Make sure that you don't send same message to multiple handlers in your code.
Message it's a linked list and your could get ANR in that case.
Get /data/anr/traces.txt to make sure that it's not ANR.
You could make sure by time in the beginning of the file.