IOException on accept thread

问题:

One part of my application connects to a device through Bluetooth and normally works fine but occasionally it won't connect and I get the following error

03-11 10:29:20.328: E/BluetoothComService(8059): accept() failed
03-11 10:29:20.328: E/BluetoothComService(8059): java.io.IOException: Operation Canceled
03-11 10:29:20.328: E/BluetoothComService(8059):    at android.bluetooth.BluetoothSocket.acceptNative(Native Method)
03-11 10:29:20.328: E/BluetoothComService(8059):    at android.bluetooth.BluetoothSocket.accept(BluetoothSocket.java:316)
03-11 10:29:20.328: E/BluetoothComService(8059):    at android.bluetooth.BluetoothServerSocket.accept(BluetoothServerSocket.java:105)
03-11 10:29:20.328: E/BluetoothComService(8059):    at android.bluetooth.BluetoothServerSocket.accept(BluetoothServerSocket.java:91)
03-11 10:29:20.328: E/BluetoothComService(8059):    at com.mypackage.name.bluetooth.BluetoothService$AcceptThread.run(BluetoothService.java:298)

This is the line where I get the exception

socket = mmServerSocket.accept();    

And this is the complete AcceptThread

private class AcceptThread extends Thread {
    // The local server socket
    private BluetoothServerSocket mmServerSocket;
    public boolean successInit = false;

    public AcceptThread() {
        closeAllConnections();

        /*
         * if(mmServerSocket != null) { try { mmServerSocket.close(); } catch
         * (IOException e) { e.printStackTrace(); } }
         */
        BluetoothServerSocket tmp = null;

        // Create a new listening server socket
        while (!successInit) {
            try {
                tmp = mAdapter
                        .listenUsingRfcommWithServiceRecord(NAME, MY_UUID);

                successInit = true;
            } catch (Exception e) {

                successInit = false;
            }
        }

        /*
         * try { tmp = mAdapter.listenUsingRfcommWithServiceRecord(NAME,
         * MY_UUID); successInit= true; } catch (IOException e) { Log.e(TAG,
         * "listen() failed", e); tmp = null; successInit = false; }
         */
        mmServerSocket = tmp;
    }

    public void run() {
        if (D)
            Log.d(TAG, "BEGIN mAcceptThread" + this);
        setName("AcceptThread");
        BluetoothSocket socket = null;

        // Listen to the server socket if we're not connected
        while (mState != STATE_CONNECTED) {
            try {
                // This is a blocking call and will only return on a
                // successful connection or an exception
                mAdapter.cancelDiscovery();

                socket = mmServerSocket.accept();
            } catch (IOException e) {
                Log.e(TAG, "accept() failed", e);
                Log.e("Error", "This isn't connecting");
                break;
            }

            // If a connection was accepted
            if (socket != null) {
                synchronized (BluetoothService.this) {
                    switch (mState) {
                    case STATE_LISTEN:
                    case STATE_CONNECTING:
                        // Situation normal. Start the connected thread.
                        connected(socket, socket.getRemoteDevice());
                        break;
                    case STATE_NONE:
                    case STATE_CONNECTED:
                        // Either not ready or already connected. Terminate new
                        // socket.
                        try {
                            socket.close();
                        } catch (IOException e) {
                            Log.e(TAG, "Could not close unwanted socket", e);
                        }
                        break;
                    }
                }
            }
        }
        if (D)
            Log.i(TAG, "END mAcceptThread");
    }

    public void cancel() {
        if (D)
            Log.d(TAG, "cancel " + this);
        try {
            mmServerSocket.close();
        } catch (IOException e) {
            Log.e(TAG, "close() of server failed", e);
        }
    }
}     

Here is the function I call at the beginning of AcceptThread in hopes to close everything to restart it

public void closeAllConnections() {
    if (mmInStream != null) {
        try {mmInStream.close();}
        catch  (Exception e){Log.e(TAG, "close() of connect socket failed", e);}
    }
    if (mmOutStream != null) {
        try {mmOutStream.close();}
        catch (Exception e){Log.e(TAG, "close() of connect socket failed", e);}
    }
    if (mmSocket != null) {
        try {
            mmSocket.close();
            //mmSocket.connect();
        }
        catch (IOException e) {
            Log.e(TAG, "close() of connect socket failed", e);
        }
    }
}

I've read through the Bluetooth Docs and SO questions but I haven't found anything that works for me and it gets a bit confusing for me as this is my first time connecting through BT.

Note

The only "fix" I have found when this happens is to turn off the BT adapter, force close the program, restart BT adapter and restart app, which is not good for obvious reasons. I tried restarting the adapter programmatically but I still can't connect.

Can anyone see what might be wrong in my BlutoothService class, which is where AcceptThread is located? Or how I would go about resolving this issue? Thanks!

Update

It does, in fact, seem like the connection is sometimes closed on one Thread and trying to reconnect on another. The problem is that I can't figure out what would cause it to try and connect on a separate Thread or how to fix it when this happens.

The only way I can successfully reproduce this is if my BT device is turned off then I turn the BT adapter off. When I turn everything back on then I get the exception and cannot connect. I have customers that it happens to randomly and periodically so I'm hoping the issues are related.

回答1:

Well, part of my problem was a hardware issue that was found out to be a problem on the third-party manufacturers end. They're firmware wasn't quite right and when it was reading the BT address, it was occasionally being corrupted.

On the software side, it was running the AcceptThread in two separate Threads periodically. What I did to fix that was to create a function to close the socket and input/output streams...

public void closeAllConnections()
    {
        if (mmInStream != null)
        {
            try {mmInStream.close();}
            catch  (Exception e){Log.e(TAG, "close() of connect socket failed", e);}
        }
        if (mmOutStream != null)
        {
            try {mmOutStream.close();}
            catch (Exception e){Log.e(TAG, "close() of connect socket failed", e);}
        }
        if (mmSocket != null)
        {
          try {
                mmSocket.close();
                Log.e("TAG", "close() of connect socket successfu;");
              } catch (IOException e) {
                   Log.e("TAG", "close() of connect socket failed", e);}
        }

Then in the BluetoothCom class, I noticed it wasn't always checking for the BT object to be null before trying to restart the service.

private void setupService() {

    // Initialize the BluetoothChatService to perform bluetooth connections
    if((mChatService != null) && (mChatService.getState() != 0)) {
        mChatService.stop();        
    }

    // I didn't have this so it would always start a new instance of the Service
    if (mChatService == null)
        mChatService = new BluetoothService(mHandler);

    mChatService.start();
}

This seems to have helped and I no longer have those problems. However, now testing on the Samsung Galaxy Tab 4 and I am once again having connection issues but only on this device. Maybe this information can help someone and I will update my answer if I figure anything else out with the new problem.

Note: As stated above, this Bluetooth app uses modified code from Android's BluetoothChat app.

Also, I have read (and noticed) that different manufacturers implement the BT stack differently which can lead to headaches (at least if yo don't know enough about it).

回答2:

Although this is old post but I recently contact same issue so I want to write down the way I solve it.

It seems your code is from Google samples BlutoothChat (as it looks same, sorry if I misunderstand). I also create my own application that base on this sample (on API level 10). I meet the accept() fail issues if I try to connect one device to other device but at the end I solve this question by simply remove some code in MainActivty

On the Google samples main activity it contain many methods when activity change (Start, Pause, etc).

Original code have this

@Override
public synchronized void onResume() {
    super.onResume();
    if(D) Log.e(TAG, "+ ON RESUME +");
    if (mChatService != null) {
        if (mChatService.getState() == ChatService.STATE_NONE) {
          mChatService.start();
        }
    }
}

This code start the Chat Service and running the AcceptThread to listening incoming connections.

When application start, this method will be call "once" and create the AcceptThread. If you do any other things that make the main activity onPause() pause (In Google samples case, if you click menu to start device_list activity the main activity will pause), when the application back to main activity it will call create AcceptThread method "one more time", this cause the problem because one thread already running but you try to interrupt it. And at the end happen accept() fail error and throw java.io.IOException: Operation Canceled error.

So to avoid this is simply remove the codes in OnResume()

@Override
public synchronized void onResume() {
    super.onResume();
    if(D) Log.e(TAG, "+ ON RESUME +");
}

or if you don't want delete any codes because you afraid cause some problem, put this code (mChatService != null) mChatService.stop(); in...

@Override
public synchronized void onPause() {
    super.onPause();
    if (mChatService != null) mChatService.stop();
    if(D) Log.e(TAG, "- ON PAUSE -");
}

Both works perfect in my project. Method 1 not create the new thread if activity resume, and Method 2 kill all the thread if you leave the current activity and disconnect all current connections if you already have one (it will start the thread again once you turn back). Method 1 wouldn't return any error but method 2 will throw accept fail again if you leave the current activity, so I suggest to use method 1.

Need to notice that this error usually happen after you modify Google samples BlutoothChat, it will never appear on the original app.

I have seen many post talk about this issue, but not see any one come out with this answer, so just want to share this. Hope this is helpful.

回答3:

That exception should occur when the BluetoothServerSocket is closed or garbage collected. I suspect that the exception is happening on an OLD copy of the thread. So something like: When you create the new thread the old thread gets cancelled and thus the BluetoothServerSocket is closed and thus accept correctly fails with that error. Check this in the debugger and/or logging on which thread the various events occur; e.g. set breakpoints on the line after accept and perhaps on the cancel function, then inspect the thread IDs there -- is the exception occurring on a previous thread?