Service discovery failed exception using Bluetooth

问题:

I'm currently working on an Android application that connects to an instrument via Bluetooth and need to write string commands and receive string responses back. Currently I have the connect/read/write working for TCP/IP over Wi-Fi and now trying to implement Bluetooth. But I am running into some roadblocks. I have been searching the web trying to find examples of something similar and haven't had any luck. I have been using the Android developer resource example: Bluetooth Chat as my main reference point.

My current code seems to work.. Then it throws a Service Discovery Failed exception at the point of the connection. I am using the DeviceListActivity class to do the discovery and selecting of the device I want to connect to. It returns anActivityResult and then my Bluetooth class waits for it to handle that and then does the connect to it. The code beneath is almost identical to the Bluetooth Chat App.

public void onActivityResult(int requestCode, int resultCode, Intent data) {
    if(!m_BluetoothAdapter.isEnabled())
    {
        m_BluetoothAdapter.enable();
    }
    switch (requestCode) {
        case REQUEST_CONNECT_DEVICE:
            // When DeviceListActivity returns with a device to connect
            if (resultCode == Activity.RESULT_OK) {
                // Get the device MAC address
                String address = data.getExtras()
                                     .getString(DeviceListActivity.EXTRA_DEVICE_ADDRESS);
                // Get the BLuetoothDevice object
                BluetoothDevice device = m_BluetoothAdapter.getRemoteDevice(address);
                // Attempt to connect to the device
                connect(device);
            }
            break;

        case REQUEST_ENABLE_BT:
            // When the request to enable Bluetooth returns
            if (resultCode == Activity.RESULT_OK) {
                // Bluetooth is now enabled, so set up a chat session
            }
            else {
                // User did not enable Bluetooth or an error occured

                Toast.makeText(this, "Bluetooth not enabled", Toast.LENGTH_SHORT).show();
                finish();
            }
    }
}

This is my connect function:

private static final UUID MY_UUID = UUID.fromString("00001101-0000-1000-8000-00805F9B34FB");

private void connect(BluetoothDevice device) {
    m_Device = device;
    BluetoothSocket tmp = null;

    // Get a BluetoothSocket for a connection with the
    // given BluetoothDevice
    try {
        tmp = device.createRfcommSocketToServiceRecord(MY_UUID);
    }
    catch (IOException e) {

    }
    m_Socket = tmp;

    m_BluetoothAdapter.cancelDiscovery();

    try {
        // This is a blocking call and will only return on a
        // successful connection or an exception
        m_Socket.connect();
    }
    catch (IOException e) {
        try {
            m_Socket.close();
        }
        catch (IOException e2) {
        }
        return;
    }
}

Hopefully, whatever I am doing wrong is simple, but I'm afraid it's never that easy. This is my first time doing any Bluetooth development, and maybe I'm doing something blatantly wrong... But I'm not sure why I get the service discovery failed exception.

You can pair/find the device at all times manually on the phone... It does require a passcode, but I don't think that is the problem that I am having.

回答1:

After three days I got it figured out thanks to some very helpful posts.

I had to replace:

tmp = device.createRfcommSocketToServiceRecord(MY_UUID);

with:

Method m = device.getClass().getMethod("createRfcommSocket", new Class[] {int.class});
         tmp = (BluetoothSocket) m.invoke(device, 1);

and voilà it works!

回答2:

As of API 15 you can use the following method:

Try replacing your UUID with the return value of getUuids() method of BluetoothDevice class. What worked for me was something like this:

UUID uuid = bluetoothDevice.getUuids()[0].getUuid();
BluetoothSocket socket = bluetoothDevice.createRfcommSocketToServiceRecord(uuid);

The reason this works is that different devices support different UUIDs and by getting the UUIDs of the device using getUuids you are supporting all features and devices.

Another interesting new method (supported since API 14) is this: BluetoothHealth.getConnectionState. Haven't tried it but looks promising...

回答3:

This was a suggested edit from an anonymous user attempting to reply to the accepted answer.

One big difference between your before and after code is the UUID you are passing. I found my answer here: http://developer.android.com/reference/android/bluetooth/BluetoothDevice.html#createRfcommSocketToServiceRecord(java.util.UUID)

I had to replace:

tmp = device.createRfcommSocketToServiceRecord(MY_UUID);

with:

private static final UUID SPP_UUID = UUID.fromString("00001101-0000-1000-8000-00805F9B34FB");
tmp = device.createRfcommSocketToServiceRecord(SPP_UUID);

and voila it works! The original code is for a peer to peer android app. It makes no sense to use the app UUID when connecting to a simple serial bluetooth device. Thats why discovery fails.

回答4:

So as it mentioned above, the point is that you need to use the UUID that the server is waiting for.

If you are connecting to a bluetooth device, such as a headset or mouse, you need to check which UUIDs the device is listening for. You can see the UUIDs like this.

UUID[] uuids = bluetoothDevice.getUuids();

And if you want to know what these UUIDs mean, see this.

回答5:

This is a realy old one question but i found that using the createInsecureRfcommSocketToServiceRecord() instead of createRfcommSocketToServiceRecord() along with the getUuids() previously mentioned do the trick for me

UUID uuid = bluetoothDevice.getUuids()[0].getUuid();
BluetoothSocket socket = bluetoothDevice.createInsecureRfcommSocketToServiceRecord(uuid);