Develop Reference

Android Bluetooth SPP - How to stop transmitting the internal send buffer ?

I am trying to control/operate a motor from an android phone in "as close as possible" realtime using the Android SPP Bluetooth socket interface. The motor ought to run in a so called 'dead man' operation mode. So the motor will only turn if a button on the android APP is touched and ought to stop immediately if the touch is released.
I implemented this by continuously sending 'keep turning' telegrams of 20 Bytes about every 20ms to keep the motor turning and to have the motor stop immediately as soon as no more telegrams are received or if a STOP telegram is received.
This seem to work acceptable well on some phone but others continue sending 'keep turning' telegrams even after the MotionEvent.ACTION_UP event has been processed and no more data are being send.
I assume that this is caused by some internal buffers that cache the transmit data and continue sending until the buffer is empty.
Simple questions:
Is there a way to purge the BT stream transmit buffer to stop all data transfer immediately?
Or can I get the fill level of the transmit buffer in which case I would not put anything more than about 2 telegrams into it?
Or is there a way to specify the buffer size when opening the stream?
Searching the net, I was not able to find anything that talks about BT stream buffer size of buffer management.
And Yes, I have implemented read and write functions as threads and I do not have any problems in reading all telegrams, and I do not need to deliver telegrams in real time but I should be able to stop sending 'keep turning' telegrams within about 50 to 100ms.
Any hints are very welcome.

I am sorry that I did not add the code, I thought it may not be necessary as it is straight forward as:
#Override
public boolean onTouch(final View v,MotionEvent event) {
int eventAction = event.getAction();
switch (eventAction) {
case MotionEvent.ACTION_DOWN:
if (v == btnUp || v == btnDown) {
// Start a thread that sends the goUP or DOWN command every 10 ms until
// btnUp released
tvCounter.setText("----");
action_touched = true;
new Thread(new Runnable() {
#Override
public void run() {
int counter = 1;
// Disable heart beat
ServiceRequest.send(EnRequest.REQ_SET_HEARTBEAT,0);
// Send GoUp command plus a wrapping counter byte every nn ms
// until the button is released
while (action_touched) {
try {
setDeadmanMove(v==btnUp,counter);
Thread.sleep(20);
++counter;
}
catch (InterruptedException ex) {
action_touched = false;
}
catch (Exception ex) {
action_touched = false;
}
}
// Send a STOP command
setDeadmanStop();
// Enable heart beat again
ServiceRequest.send(EnRequest.REQ_SET_HEARTBEAT,1);
// We are done
}
}).start();
}
break;
case MotionEvent.ACTION_UP:
// Stop Thread
action_touched = false;
break;
}
return true;
}
The snipped below is part of the communication class that manages the Bluetooth serial communication.
public void btWrite(DeviceRecord message) {
if (runBTreceiver) {
if (message.isValidRecord()) {
try {
lock.lock();
++lockCounter;
mmBufferedOut.write(message.getFullRecord());
mmBufferedOut.flush();
}
catch (IOException e) {
if (GlobalData.isDebugger) Log.i(TAG, "Failed sending " + message + " " + e.getMessage());
ServiceResponse.send(EnEvent.EVT_BT_RECEIVER_ERROR, "Error data send: " + e.getMessage());
resetConnection();
runBTreceiver=false;
}
finally {
--lockCounter;
lock.unlock();
}
}
}
}
The code snipped that allocates and opens the Bluetooth connection
try {
// Set up a pointer to the remote node using it's address.
BluetoothDevice device = myBluetoothAdapter.getRemoteDevice(myBluetoothMacId);
if (device != null)
{
// Two things are needed to make a connection:
// A MAC address, which we got above.
// A Service ID or UUID. In this case we are using the
// UUID for SPP.
try {
myBluetoothSocket = device.createRfcommSocketToServiceRecord(GlobalData.MY_UUID);
}
catch (IOException e) {
sendEventStatus(EnEvent.EVT_BTADAPTER_FAIL,
String.format(GlobalData.rString(R.string.srv_failcrt),BTERROR_CREATE,e.getMessage()));
}
// Establish the connection. This will block until it connects or
// timeout?
try {
if (! myBluetoothSocket.isConnected()) {
myBluetoothSocket.connect();
}
}
catch (IOException e) {
try {
Log.e("","trying fallback...");
myBluetoothSocket =(BluetoothSocket) device.getClass().getMethod("createRfcommSocket", new Class[] {int.class}).invoke(device,1);
myBluetoothSocket.connect();
}
catch (IOException e2) {
sendEventStatus(EnEvent.EVT_BTADAPTER_FAIL,e2.getMessage());
}
}
}
else {
sendEventStatus(EnEvent.EVT_BTADAPTER_FAIL,
String.format(GlobalData.rString(R.string.srv_failcrt),BTERROR_DEVICE,"getRemoteDevice failed"));
}
}
catch (Exception e) {
sendEventStatus(EnEvent.EVT_BTADAPTER_FAIL, e.getMessage());
return;
}
InputStream tmpIn = null;
OutputStream tmpOut = null;
mmSocket = socket;
// Get the input and output streams, using temp objects because
// member streams are final
try {
tmpIn = socket.getInputStream();
tmpOut = socket.getOutputStream();
}
catch (IOException e) {
ServiceResponse.send(EnEvent.EVT_ERROR, GlobalData.rString(R.string.srv_failcst) + e.getMessage());
resetConnection();
runBTreceiver=false;
}
mmInStream = tmpIn;
// mmOutStream = tmpOut;
mmBufferedOut = new BufferedOutputStream(tmpOut,80);
// Initial request
btWrite(new DeviceRecord(0, 4));
I have never discovered any problems sending and receiving data via this code. All records are sent and received properly. Only problem was that I am unable to purge the transmit buffer at the moment the operate button was released.
To overcome this problem, I have changed the protocol in such a way, that only a single 'keep turning' telegram is send at a time, the next telegram will be send after a response from the other end (sort of handshaking), the program then continue to run this ping/pong until the button is released.
This method works quite well as the transmit buffer will never hold more than one telegram at a time.
the mentioned problem is solved though but I still have no clue of whether it would be possible to purge a transmit buffer

Android Bluetooth InputStream real time read

I am working on an Android application that receives a real time data by Bluetooth and plots it on the screen.
The data is a gyro sensor position information. I am sending it from a custom Freescale Kinetis K10 microcontroller board (designed and tested by myself). For the Bluetooth communication I am using HC-05 Bluetooth module.
The format of the data is as follows:
byte_1: position identification byte, always equals to -128
byte_2: position of axis 1
byte_3: position of axis 2
byte_4: position of axis 3
I am sending these 4 bytes continuously one after another, in that particular order. I am sending this packet of 4 bytes every 5 ms and sending the packet takes about 4.7 ms (9600 baud rate).
The data output from the microcontroller is perfect in terms of accuracy and timing (checked with a logic analyzer).
The problem is that when it is being received from the phone, some of the bytes seem to get lost. Here is the part of the code, where I am reading the InputStream:
private class ConnectedThread extends Thread {
private final BluetoothSocket mmSocket;
private final InputStream mmInStream;
private final OutputStream mmOutStream;
public ConnectedThread(BluetoothSocket socket) {
mmSocket = socket;
InputStream tmpIn = null;
OutputStream tmpOut = null;
try {
tmpIn = socket.getInputStream();
tmpOut = socket.getOutputStream();
} catch (IOException e) {
Log.e("Printer Service", "temp sockets not created", e);
}
mmInStream = tmpIn;
mmOutStream = tmpOut;
}
#Override
public void run() {
Log.i("BluetoothService", "BEGIN mConnectedThread");
byte[] buffer = new byte[4];
int bytes;
while (true) {
try {
bytes = mmInStream.read(buffer);
int position = 0;
if(buffer[0] == -128) {
if(bytes >= 2) {
sendArray.errorTilt = buffer[1];
}
if(bytes >= 3) {
sendArray.errorRoll = buffer[2];
}
if(bytes == 4) {
sendArray.errorPan = buffer[3];
}
}
else if(buffer[1] == -128) {
position = 1;
if(bytes >= 3) {
sendArray.errorTilt = buffer[2];
}
if(bytes == 4) {
sendArray.errorRoll = buffer[3];
}
if(bytes >= 2) {
sendArray.errorPan = buffer[0];
}
}
else if(buffer[2] == -128 && bytes >= 3) {
position = 2;
sendArray.errorRoll = buffer[0];
sendArray.errorPan = buffer[1];
if(bytes == 4) {
sendArray.errorTilt = buffer[3];
}
}
else if(buffer[3] == -128 && bytes == 4) {
position = 3;
sendArray.errorTilt = buffer[0];
sendArray.errorRoll = buffer[1];
sendArray.errorPan = buffer[2];
}
if(position <= bytes && bytes > 1) {
sendArray.errorUpdate = true;
}
} catch (Exception e) {
e.printStackTrace();
connectionLost();
BluetoothService.this.stop();
break;
}
}
}
public void write(int oneByte) {
try {
mmOutStream.write(oneByte);
} catch (IOException e) {
Log.e("BluetoothService", "Exception during write", e);
}
}
public void cancel() {
try {
mmSocket.close();
} catch (IOException e) {
Log.e("BluetoothService", "close() of connect socket failed", e);
}
}
}
sendArray is a singleton that keeps many different variables.
errorTilt, errorRoll and errorPan are the current values of the axis, which are being updated from the receiving buffer.
"position" keeps the position of the position identification byte. It is used for a check if any variables have been updated.
Many times just one byte is received in the input buffer and since I don't know which axis is that supposed to be, since I don't have information about it's relative position to the position byte, this particular byte is useless and gets lost.
I've tested the accuracy of receiving by the following method. I made the MCU output a triangular wave on one of the axis, instead of the axis data. On the phone the lines of the triangular wave are not straight as they are supposed to be, but randomly curved and containing artifacts.
To plot the data I am using GraphView and I am updating the graph on equal intervals from a separate thread.
I've tried using longer receiving buffer (with a modified receiving algorithm), but this doesn't help as only a few bytes are being received at a time.
I've tried implementing InputStream.available() but it was always giving 127 bytes available, which didn't seem to be true.
I've read many threads about similar problems and I spent the last 5 days working on it, but I couldn't find a good solution.
To summarize, I need to achieve accurate, real time (or close to real time) receiving of all the bytes.
Thread with a similar problem:
How to do good real-time data streaming using Java Android SDK
Thank you.
UPDATE:
I've tried sending the information just for one of the axis, so it is simple and clear, without the need of position bytes. I was sending it again every 5 ms, but this time it was more time between the consecutive bytes, since it's just one byte in the packet.
I used InputStream.read() this time, which doesn't require a buffer. However, the incoming data was corrupted again, because random bytes couldn't be received.
I've seen different project using this method successfully, I don't know why it's not working with me. I thought it might be a problem with the HC-05 Bluetooth module I'm using, but I tried a different one - HC-06, and the situation is the same. I haven't tried a different phone, but my phone (Samsung Galaxy S3, Android 4.1.2) seems to be working OK.
UPDATE2: I've tried again testing the original code with InputStream.available() before reading from the stream.
When the condition is available()>0, there are no major changes, maybe it works slightly worse.
When the condition is available()>1, it never reads. I guess that is because of the unreliable available() method, as it says in the documentation.

you have incorrect processing of data, if you want to get data from microcontroller board. You have to use bytesAvaliable because android bluetooth Socket is pretty slow over microcontroller boards with bluetooth. But "bytesAvaliable way" has nuance - As socket is slow receiver, bytesAvaliable can catch more then 1 packet from board in one time so you gotta devide readed data by yourself, Check my code out below! My code is getting 38 bytes packets from inertial sensor so you gotta only change count of bytes! 0xAA is the first byte of every next packet so if you find 0xAA byte and have 38 bytes you get packet and nullify iterator. But anyway I'm sure that you still can sometimes lose data because it's not high frequency data transfering way
public void run() {
byte[] bytes = new byte[38];
int iterator = 0;
while (true) {
try {
int bytesAvailable = mmInStream.available();
if (bytesAvailable > 0) {
byte[] curBuf = new byte[bytesAvailable];
mmInStream.read(curBuf);
for (byte b : curBuf) {
if (b == (byte) 0xAA && iterator == 38) {
mHandler.obtainMessage(MainActivity.DATA_READ, bytes.length, -1, bytes).sendToTarget();
iterator = 0;
bytes[iterator] = b;
} else {
bytes[iterator] = b;
}
iterator++;
}
}
} catch (IOException ex) {
Log.e(TAG, "disconnected", ex);
connectionLost();
break;
}
}
}

android bluetoothsocket receive zero-value bytes?

Got a problem at receiving bytes from bluetooth socket. I'm trying to send message created by arduino - couple of single bytes values i.e. 0x41, 0x05, 0xFF(...) into my phone with android. It works fine until one of these value is zero (0x00). Transmission hangs until new message comes. Anyone meet with that situation?
My "reader" works in separate thread, processBuffer() do sth with data that should be received:
public void run() {
while(stop == false){
try {
bytes = InStream.read(readbuffer);
for (int i = 0; i < bytes; i++){
Log.d("FRAME", "Read bytes "+readbuffer[i]);
}
Log.d("FRAME", "Read number of bytes "+bytes);
processBuffer(bytes);
} catch (Exception e){
Log.d("BT_debug", "Cannot read bytes");
Log.d("BT_debug", "iterator: "+iterator);
e.printStackTrace();
break;
}
}
}

Android VpnService to capture packets won't capture packets

I been searching for my answer for a couple of hours now and I can't figure it out. Please help.
What I want to do is to use the VpnService in Android to grab network packets like the application tPacketCapture
I started by using the ToyVpn sample code from google and modifying it so I don't send the data to a server. However, I'm not sure if this is correct.
My configure method uses the wlan ip address for binder.addAddress() before calling establish(). I am using a nexus 7 and I used "adb shell netcfg | grep wlan0" to get the address:
wlan0 UP 192.168.0.6/24 0x00001043 10:bf:48:bf:5f:9d
And add it in my method:
private void configure() 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();
builder.setMtu(1500);
builder.addAddress("192.168.0.6", 24);
try {
mInterface.close();
} catch (Exception e) {
// ignore
}
mInterface = builder.establish();
}
After calling this, I call the run method which I modified to pass a String instead of a InetSocketAddress and this is not important because I am not using it anywhere:
private void run(String run) throws Exception {
configure();
FileInputStream in = new FileInputStream(mInterface.getFileDescriptor());
// Allocate the buffer for a single packet.
ByteBuffer packet = ByteBuffer.allocate(32767);
// We use a timer to determine the status of the tunnel. It
// works on both sides. A positive value means sending, and
// any other means receiving. We start with receiving.
int timer = 0;
// We keep forwarding packets till something goes wrong.
while (true) {
// 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) {
Log.i(TAG,"************new packet");
while (packet.hasRemaining()) {
Log.i(TAG,""+packet.get());
//System.out.print((char) packet.get());
}
// 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;
}
}
}
}
When I do adb logcat, nothing is happening. Am I going about this correctly? I feel like I am missing something.
Thank you!
EDIT:
From the logs I see the following lines:
I/ActivityManager( 460): START u0 {act=android.intent.action.MAIN cat=[android.intent.category.LAUNCHER] flg=0x10000000 cmp=com.example.android.toyvpn/.ToyVpnClient} from pid 10247
I/ActivityManager( 460): Start proc com.example.android.toyvpn for activity com.example.android.toyvpn/.ToyVpnClient: pid=10287 uid=10122 gids={50122, 3003, 1028}
I/ActivityManager( 460): Displayed com.example.android.toyvpn/.ToyVpnClient: +1s144ms
I/Vpn ( 460): Switched from [Legacy VPN] to com.example.android.toyvpn
D/Vpn ( 460): setting state=IDLE, reason=prepare
I/ToyVpnService(10287): running vpnService
D/Vpn ( 460): setting state=CONNECTING, reason=establish
D/VpnJni ( 460): Address added on tun0: 192.168.0.6/24
I/Vpn ( 460): Established by com.example.android.toyvpn.ToyVpnService on tun0
W/ContextImpl( 460): Calling a method in the system process without a qualified user: android.app.ContextImpl.bindService:1406 com.android.server.connectivity.Vpn.establish:289 com.android.server.ConnectivityService.establishVpn:3263 android.net.IConnectivityManager$Stub.onTransact:504 android.os.Binder.execTransact:351
D/Vpn ( 460): setting state=AUTHENTICATING, reason=establish
So it seems to be connecting.
Full source:
public class ToyVpnService extends VpnService implements Handler.Callback, Runnable {
private static final String TAG = "ToyVpnService";
private Handler mHandler;
private Thread mThread;
private ParcelFileDescriptor mInterface;
#Override
public int onStartCommand(Intent intent, int flags, int startId) {
// 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();
}
// Start a new session by creating a new thread.
mThread = new Thread(this, "ToyVpnThread");
mThread.start();
return START_STICKY;
}
#Override
public void onDestroy() {
if (mThread != null) {
mThread.interrupt();
}
}
#Override
public boolean handleMessage(Message message) {
if (message != null) {
Toast.makeText(this, message.what, Toast.LENGTH_SHORT).show();
}
return true;
}
#Override
public synchronized void run() {
Log.i(TAG,"running vpnService");
try {
runVpnConnection();
} catch (Exception e) {
e.printStackTrace();
//Log.e(TAG, "Got " + e.toString());
} finally {
try {
mInterface.close();
} catch (Exception e) {
// ignore
}
mInterface = null;
mHandler.sendEmptyMessage(R.string.disconnected);
Log.i(TAG, "Exiting");
}
}
private boolean runVpnConnection() throws Exception {
configure();
FileInputStream in = new FileInputStream(mInterface.getFileDescriptor());
// Allocate the buffer for a single packet.
ByteBuffer packet = ByteBuffer.allocate(32767);
// We keep forwarding packets till something goes wrong.
while (true) {
// 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) {
Log.i(TAG,"************new packet");
System.exit(-1);
while (packet.hasRemaining()) {
Log.i(TAG,""+packet.get());
//System.out.print((char) packet.get());
}
packet.limit(length);
// tunnel.write(packet);
packet.clear();
// There might be more outgoing packets.
idle = false;
}
Thread.sleep(50);
}
}
public String getLocalIpAddress()
{
try {
for (Enumeration<NetworkInterface> en = NetworkInterface.getNetworkInterfaces(); en.hasMoreElements();) {
NetworkInterface intf = en.nextElement();
for (Enumeration<InetAddress> enumIpAddr = intf.getInetAddresses(); enumIpAddr.hasMoreElements();) {
InetAddress inetAddress = enumIpAddr.nextElement();
Log.i(TAG,"****** INET ADDRESS ******");
Log.i(TAG,"address: "+inetAddress.getHostAddress());
Log.i(TAG,"hostname: "+inetAddress.getHostName());
Log.i(TAG,"address.toString(): "+inetAddress.getHostAddress().toString());
if (!inetAddress.isLoopbackAddress()) {
//IPAddresses.setText(inetAddress.getHostAddress().toString());
Log.i(TAG,"IS NOT LOOPBACK ADDRESS: "+inetAddress.getHostAddress().toString());
return inetAddress.getHostAddress().toString();
} else{
Log.i(TAG,"It is a loopback address");
}
}
}
} catch (SocketException ex) {
String LOG_TAG = null;
Log.e(LOG_TAG, ex.toString());
}
return null;
}
private void configure() 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();
builder.setMtu(1500);
builder.addAddress("192.168.0.6", 24);
try {
mInterface.close();
} catch (Exception e) {
// ignore
}
mInterface = builder.establish();
}
}

Ok, it was not easy at all but I figured out how to capture packets. Since I am not extremely familiar with networking (but this new job is requesting that I am) I had difficulty with setting everything correctly. Basically after setting the right route in the VpnService.builder I got to receiving packets correctly.
So:
builder.addAddress("192.168.0.6", 24); // was wrong, you need to put an internal IP (10.0.2.0 for example)
and
builder.addRoute("0.0.0.0", 0); // needs to be this.
you don't need to set up a DnsServer through builder.addDnsServer() to make it work. Hope this helps anyone!

My configure method uses the wlan ip address for binder.addAddress() before >calling establish(). I am using a nexus 7 and I used "adb shell netcfg | grep >wlan0" to get the address:
wlan0 UP 192.168.0.6/24 0x00001043 10:bf:48:bf:5f:9d
I have wrote a simple script in python to show you netcfg graphically from adb.
It is updating every second.
https://github.com/ilanben/graphical_netcfg
Enjoy :)

Network timed out exception

I have an Android application which connects to an Arduino server and sends it sockets on a button press, but as soon as I press the button it waits a little while and then throws "Connection timed out". I know the Arduino works; I tried it over the browser and it was fine. Why can't my application access it?
The Android code:
Button.OnClickListener buttonConnectOnClickListener = new Button.OnClickListener() {
public void onClick(View v) {
Log.i(Tag,"connecting to Server");
try {
Log.i(Tag,"Enters try");
socket = new Socket("161.53.168.112", 8888);
Log.i(Tag,"stvorio socket");
dataOutputStream = new DataOutputStream(socket.getOutputStream());//and stream
Log.i(Tag,"Writing 1 on socket.");
dataOutputStream.writeBytes("1");
}
catch (UnknownHostException e) {
Log.i(Tag,e.toString());
}
catch (IOException e) {
Log.i(Tag,e.toString());
}
catch (Exception e) {
Log.e(Tag, e.toString());
And here is the code used in the Arduino. It's quite simple, so I can't understand what went wrong. I used many logs, because I wanted to see where the mistake is. I use my Arduino as a server and post something on it. If I type in 161.53.168.112:8888 in a web browser, it finds it and can send a request but my Android phone gets nothing, even using the browser, and not an app. I can't access my server. AM I maybe missing some permission in the server or on the Android?
byte mac[] = { 0x90, 0xA2, 0xDA, 0x00, 0x36, 0xFF };
byte ip[] = { 161, 53, 168, 114 };
int serverPort = 8888;
#define kitchenLight = 9;
Server server(serverPort);
void setup()
{
Serial.begin(9600);
Ethernet.begin(mac, ip, gateway, subnet);
pinMode(kitchenLight,OUTPUT);
server.begin();
}
void loop()
{
Client client = server.available();
if(client)
{
while(client.connected()) {
if(client.available()) {
char c = client.read();
appMessage += c;
if (c == '\n')
{
Serial.println("Message from Client: "+appMessage);
if(appMessage.IndexOf("kitchenLight1") != -1)
{
digitalWrite(kitchenLight,HIGH);
}
}
}
}
}
client.close();
}

After you make a connection between your Arduino and Android, you should add a delay, like, for a second or two (more likely two), because it takes that time for Arduino to get ready receiving commands.
Hope this helps :)