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copied!<p>I have finally found a workaround. The magic is hidden under the hood of the <code>BluetoothDevice</code> class (see <a href="https://github.com/android/platform_frameworks_base/blob/android-4.3_r2/core/java/android/bluetooth/BluetoothDevice.java#L1037" rel="noreferrer">https://github.com/android/platform_frameworks_base/blob/android-4.3_r2/core/java/android/bluetooth/BluetoothDevice.java#L1037</a>).</p> <p>Now, when I receive that exception, I instantiate a fallback <code>BluetoothSocket</code>, similar to the source code below. As you can see, invoking the hidden method <code>createRfcommSocket</code> via reflections. I have no clue why this method is hidden. The source code defines it as <code>public</code> though...</p> <pre><code>Class<?> clazz = tmp.getRemoteDevice().getClass(); Class<?>[] paramTypes = new Class<?>[] {Integer.TYPE}; Method m = clazz.getMethod("createRfcommSocket", paramTypes); Object[] params = new Object[] {Integer.valueOf(1)}; fallbackSocket = (BluetoothSocket) m.invoke(tmp.getRemoteDevice(), params); fallbackSocket.connect(); </code></pre> <p><code>connect()</code> then does not fail any longer. I have experienced a few issues still. Basically, this sometimes blocks and fails. Rebooting the SPP-Device (plug off / plug in) helps in such cases. Sometimes I also get another Pairing request after <code>connect()</code> even when the device is already bonded.</p> <p>UPDATE:</p> <p>here is a complete class, containing some nested classes. for a real implementation these could be held as seperate classes.</p> <pre><code>import java.io.IOException; import java.io.InputStream; import java.io.OutputStream; import java.lang.reflect.Method; import java.util.List; import java.util.UUID; import android.bluetooth.BluetoothAdapter; import android.bluetooth.BluetoothDevice; import android.bluetooth.BluetoothSocket; import android.util.Log; public class BluetoothConnector { private BluetoothSocketWrapper bluetoothSocket; private BluetoothDevice device; private boolean secure; private BluetoothAdapter adapter; private List<UUID> uuidCandidates; private int candidate; /** * @param device the device * @param secure if connection should be done via a secure socket * @param adapter the Android BT adapter * @param uuidCandidates a list of UUIDs. if null or empty, the Serial PP id is used */ public BluetoothConnector(BluetoothDevice device, boolean secure, BluetoothAdapter adapter, List<UUID> uuidCandidates) { this.device = device; this.secure = secure; this.adapter = adapter; this.uuidCandidates = uuidCandidates; if (this.uuidCandidates == null || this.uuidCandidates.isEmpty()) { this.uuidCandidates = new ArrayList<UUID>(); this.uuidCandidates.add(UUID.fromString("00001101-0000-1000-8000-00805F9B34FB")); } } public BluetoothSocketWrapper connect() throws IOException { boolean success = false; while (selectSocket()) { adapter.cancelDiscovery(); try { bluetoothSocket.connect(); success = true; break; } catch (IOException e) { //try the fallback try { bluetoothSocket = new FallbackBluetoothSocket(bluetoothSocket.getUnderlyingSocket()); Thread.sleep(500); bluetoothSocket.connect(); success = true; break; } catch (FallbackException e1) { Log.w("BT", "Could not initialize FallbackBluetoothSocket classes.", e); } catch (InterruptedException e1) { Log.w("BT", e1.getMessage(), e1); } catch (IOException e1) { Log.w("BT", "Fallback failed. Cancelling.", e1); } } } if (!success) { throw new IOException("Could not connect to device: "+ device.getAddress()); } return bluetoothSocket; } private boolean selectSocket() throws IOException { if (candidate >= uuidCandidates.size()) { return false; } BluetoothSocket tmp; UUID uuid = uuidCandidates.get(candidate++); Log.i("BT", "Attempting to connect to Protocol: "+ uuid); if (secure) { tmp = device.createRfcommSocketToServiceRecord(uuid); } else { tmp = device.createInsecureRfcommSocketToServiceRecord(uuid); } bluetoothSocket = new NativeBluetoothSocket(tmp); return true; } public static interface BluetoothSocketWrapper { InputStream getInputStream() throws IOException; OutputStream getOutputStream() throws IOException; String getRemoteDeviceName(); void connect() throws IOException; String getRemoteDeviceAddress(); void close() throws IOException; BluetoothSocket getUnderlyingSocket(); } public static class NativeBluetoothSocket implements BluetoothSocketWrapper { private BluetoothSocket socket; public NativeBluetoothSocket(BluetoothSocket tmp) { this.socket = tmp; } @Override public InputStream getInputStream() throws IOException { return socket.getInputStream(); } @Override public OutputStream getOutputStream() throws IOException { return socket.getOutputStream(); } @Override public String getRemoteDeviceName() { return socket.getRemoteDevice().getName(); } @Override public void connect() throws IOException { socket.connect(); } @Override public String getRemoteDeviceAddress() { return socket.getRemoteDevice().getAddress(); } @Override public void close() throws IOException { socket.close(); } @Override public BluetoothSocket getUnderlyingSocket() { return socket; } } public class FallbackBluetoothSocket extends NativeBluetoothSocket { private BluetoothSocket fallbackSocket; public FallbackBluetoothSocket(BluetoothSocket tmp) throws FallbackException { super(tmp); try { Class<?> clazz = tmp.getRemoteDevice().getClass(); Class<?>[] paramTypes = new Class<?>[] {Integer.TYPE}; Method m = clazz.getMethod("createRfcommSocket", paramTypes); Object[] params = new Object[] {Integer.valueOf(1)}; fallbackSocket = (BluetoothSocket) m.invoke(tmp.getRemoteDevice(), params); } catch (Exception e) { throw new FallbackException(e); } } @Override public InputStream getInputStream() throws IOException { return fallbackSocket.getInputStream(); } @Override public OutputStream getOutputStream() throws IOException { return fallbackSocket.getOutputStream(); } @Override public void connect() throws IOException { fallbackSocket.connect(); } @Override public void close() throws IOException { fallbackSocket.close(); } } public static class FallbackException extends Exception { /** * */ private static final long serialVersionUID = 1L; public FallbackException(Exception e) { super(e); } } } </code></pre>

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