Java. io. IOException, “bad file number” USB connection

I'm setting up a USB connection between my Android phone and another device Now just send bytes to test I get some clear communication, but it always ends up in Java io. IOException: write failure: ebadf (wrong file number) "after one second, sometimes reading remains alive, but writing dies; the other two die

I didn't do anything super fancy, read and write like Google Docs:

Initial connection (in the broadcast receiver, I know this part is at least initial)

if (action.equals(ACTION_USB_PERMISSION))
{
    ParcelFileDescriptor pfd = manager.openAccessory(accessory);
    if (pfd != null) {
        FileDescriptor fd = pfd.getFileDescriptor();
        mIn = new FileInputStream(fd);
        mOut = new FileOutputStream(fd);
    }
}

Read:

Thread thread = new Thread(new Runnable() {
    @Override
    public void run() {
        byte[] buf = new byte[BUF_SIZE];
        while (true)
        {
            try {
                int recvd = mIn.read(buf);
                if (recvd > 0) {
                    byte[] b = new byte[recvd];
                    System.arraycopy(buf,b,recvd);
                    //Parse message
                }
            }
            catch (IOException e) {
                Log.e("read error","Failed to read from stream");
                e.printStackTrace();
            }
        }
    }
});
thread.start();

Writing:

synchronized(mWriteLock) {
    if (mOut !=null && byteArray.length>0) {
        try {
            //mOut.flush();
            mOut.write(byteArray,byteArray.length);
        }
        catch (IOException e) {
            Log.e("error","error writing");
            e.printStackTrace();
            return false;
        }
    }
    else {
        Log.e(TAG,"Can't send data,serial stream is null");
        return false;
    }
}

Error stack trace:

java.io.IOException: write Failed: EBADF (Bad file number)
W/System.err(14028):     at libcore.io.IoBridge.write(IoBridge.java:452)
W/System.err(14028):     at java.io.FileOutputStream.write(FileOutputStream.java:187)
W/System.err(14028):     at com.my.android.transport.MyUSBService$5.send(MyUSBService.java:468)
W/System.err(14028):     at com.my.android.transport.MyUSBService$3.onReceive(MyUSBService.java:164)
W/System.err(14028):     at android.app.LoadedApk$ReceiverDispatcher$Args.run(LoadedApk.java:781)
W/System.err(14028):     at android.os.Handler.handleCallback(Handler.java:608)
W/System.err(14028):     at android.os.Handler.dispatchMessage(Handler.java:92)
W/System.err(14028):     at android.os.Looper.loop(Looper.java:156)
W/System.err(14028):     at android.app.ActivityThread.main(ActivityThread.java:5045)
W/System.err(14028):     at java.lang.reflect.Method.invokeNative(Native Method)
W/System.err(14028):     at java.lang.reflect.Method.invoke(Method.java:511)
W/System.err(14028):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
W/System.err(14028):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
W/System.err(14028):     at dalvik.system.NativeStart.main(Native Method)
W/System.err(14028): Caused by: libcore.io.ErrnoException: write Failed: EBADF (Bad file number)
W/System.err(14028):     at libcore.io.Posix.writeBytes(Native Method)
W/System.err(14028):     at libcore.io.Posix.write(Posix.java:178)
W/System.err(14028):     at libcore.io.BlockGuardOs.write(BlockGuardOs.java:191)
W/System.err(14028):     at libcore.io.IoBridge.write(IoBridge.java:447)
W/System.err(14028):     ... 13 more

I've recorded the whole place, so I know it's not obvious, such as receiving another license request (so the file stream is reinitialized as an intermediate read) The stream is also not closed because I have never happened anywhere in my code (now) I don't get any separate or attached events (I record if it happens) Nothing seems too common; It's just dead

I thought it might be a concurrency problem, so I played with locks and slept without any work, I tried I don't think this is a throughput problem because it still happens every time I read (at both ends) and read a single packet at a time (ultra slow bit rate) Does the buffer have a chance to overspend at the other end? How can I solve this problem? I can access the code at the other end, which is also an Android device, using host mode If it is important, I can publish this code - standard batch transfer

Does the phone lack support for Android accessory mode? I tried two mobile phones and they failed, so I suspect so

I want to know why this error is usually caused when writing or reading from USB on Android?

Solution

It eventually becomes a threading problem I need to separate and even write better than reading

I'm based on this code