Sending data via bluetooth via SPP using an Android device

Question

I am trying to send data from an Android device to a remote Bluetooth device that supports a serial port profile (SPP). I notice that every time I open and close a socket after each button click, it works too slowly. What socket commands should run in the Run () and Onclick () functions? The following is the class that performs Bluetooth IO:

public class Selecteddevice extends Activity implements OnClickListener { private static final String TAG = "THINBTCLIENT"; private BluetoothAdapter mBluetoothAdapter = null; private BluetoothDevice device; private BluetoothSocket btSocket = null; private OutputStream outStream = null; private static final UUID MY_UUID = UUID.fromString("00001101-0000-1000-8000-00805F9B34FB"); public static String address; @Override public void onCreate(Bundle savedInstanceState) { // TODO Auto-generated method stub super.onCreate(savedInstanceState); this.setContentView(R.layout.selecteddevice); findViewById(R.id.toggleButton1).setOnClickListener(this); findViewById(R.id.toggleButton2).setOnClickListener(this); findViewById(R.id.toggleButton3).setOnClickListener(this); } @Override public void onStart() { super.onStart(); String address = getIntent().getStringExtra("address"); TextView tv1 = (TextView) findViewById(R.id.textView_address); tv1.setText(" DEVICE ADDRESS: " + address); mBluetoothAdapter = BluetoothAdapter.getDefaultAdapter(); device = mBluetoothAdapter.getRemoteDevice(address); run(); } public void run(){ mBluetoothAdapter.cancelDiscovery(); try { btSocket = device.createRfcommSocketToServiceRecord(MY_UUID); } catch (IOException e) { Log.e(TAG, "ON START: Socket creation failed.", e); } try { btSocket.connect(); } catch (IOException e) { Log.e(TAG, "sendTestByte: Socket connection failed.", e); } } public void sendTestString(String s){ try { outStream = btSocket.getOutputStream(); } catch (IOException e) { Log.e(TAG, "sendTestByte: OutputStream creation failed.", e); } try { outStream.write(s.getBytes()); Log.d(TAG, "sendTestByte: OutputStream write succeeded."); } catch (IOException e) { Log.e(TAG, "sendTestByte: OutputStream writefailed.", e); } } public void onClick(View v){ switch(v.getId()) { case R.id.toggleButton1: this.sendTestString("1"); break; case R.id.toggleButton2: this.sendTestString("2"); break; case R.id.toggleButton3: this.sendTestString("3"); break; } } @Override public void onPause() { super.onPause(); if (outStream != null) { try { outStream.flush(); } catch (IOException e5) { Log.e(TAG, "ON PAUSE: Couldn't flush output stream.", e5); } } try { btSocket.close(); } catch (IOException e6) { Log.e(TAG, "ON PAUSE: Unable to close socket.", e6); } } @Override public void onStop() { super.onStop(); } @Override public void onDestroy() { super.onDestroy(); } 

}

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My program crashes after pairing with the error message:

  07-27 13:00:57.483: E/THINBTCLIENT(7855): sendTestByte: OutputStream writefailed. 07-27 13:00:57.483: E/THINBTCLIENT(7855): java.io.IOException: socket closed 07-27 13:00:57.483: E/THINBTCLIENT(7855): at android.bluetooth.BluetoothSocket.write(BluetoothSocket.java:331) ... 

What am I doing wrong?

Thanks.

Answer 1

If you are sure that the connection is established without any errors and you can get the socket, try assigning your OutputStream member in the run() method as follows:

 public void run() { mBluetoothAdapter.cancelDiscovery(); try { btSocket = device.createRfcommSocketToServiceRecord(MY_UUID); } catch (IOException e) { Log.e(TAG, "ON START: Socket creation failed.", e); } try { btSocket.connect(); } catch (IOException e) { Log.e(TAG, "sendTestByte: Socket connection failed.", e); } try { outStream = btSocket.getOutputStream(); } catch (IOException e) { Log.e(TAG, "sendTestByte: OutputStream creation failed.", e); } } public void sendTestString(String s) { try { outStream.write(s.getBytes()); outSttream.flush(); // <-- Try flush to force sending data in buffer Log.d(TAG, "sendTestByte: OutputStream write succeeded."); } catch (IOException e) { Log.e(TAG, "sendTestByte: OutputStream writefailed.", e); } } 

You are not actually closing the socket, but this should work. Make sure that the connection to the master is not lost before calling write()