Hi,
 
I developed an android app that uses bluetooth connection to print receipts through iMZ320 printers, everything works great on Android 4.x, yet on a tablet with Lollipop logs these errors:
 
02-06 17:40:10.790 18479 18498 W System.err: com.zebra.sdk.comm.ConnectionException: Could not connect to device: read failed, socket might closed or timeout, read ret: -1
02-06 17:40:10.790 18479 18498 W System.err:     at com.zebra.sdk.comm.ConnectionA.open(Unknown Source)
02-06 17:40:10.790 18479 18498 W System.err:     at com.zebra.sdk.comm.BluetoothConnection.open(Unknown Source)
02-06 17:40:10.790 18479 18498 W System.err:     at com.labinf.gestioneagenti.oggetti.Printer.connect(Printer.java:51)
02-06 17:40:10.790 18479 18498 W System.err:     at com.labinf.gestioneagenti.threads.PrintAT.doInBackground(PrintAT.java:57)
02-06 17:40:10.790 18479 18498 W System.err:     at com.labinf.gestioneagenti.threads.PrintAT.doInBackground(PrintAT.java:1)
02-06 17:40:10.790 18479 18498 W System.err:     at android.os.AsyncTask$2.call(AsyncTask.java:288)
02-06 17:40:10.790 18479 18498 W System.err:     at java.util.concurrent.FutureTask.run(FutureTask.java:237)
02-06 17:40:10.790 18479 18498 W System.err:     at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:231)
02-06 17:40:10.790 18479 18498 W System.err:     at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)
02-06 17:40:10.790 18479 18498 W System.err:     at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
02-06 17:40:10.790 18479 18498 W System.err:     at java.lang.Thread.run(Thread.java:818)
02-06 17:40:10.790 18479 18498 W System.err: Caused by: com.zebra.sdk.comm.ConnectionException: read failed, socket might closed or timeout, read ret: -1
02-06 17:40:10.790 18479 18498 W System.err:     at com.zebra.sdk.comm.internal.BluetoothInsecureZebraConnectorImpl.tryPublicApiWay(Unknown Source)
02-06 17:40:10.790 18479 18498 W System.err:     at com.zebra.sdk.comm.internal.BluetoothInsecureZebraConnectorImpl.open(Unknown Source)
02-06 17:40:10.790 18479 18498 W System.err:     ... 11 more
 
These errors show off when:
 
printerConnection = new BluetoothConnectionInsecure(PRINTER_ADDRESS);
        try {
            printerConnection.open();
            Logger.log(zebra_tag, "Connected");
        } catch (ConnectionException e) {
            Logger.log(zebra_tag, "Comm Error! Disconnecting");
            e.printStackTrace();
            // DemoSleeper.sleep(1000);
            disconnect();
        }
 
The PRINTER_ADDRESS is saved this way:
 
1) get the list of devices available
new Thread(new Runnable() {
            public void run() {
                Looper.prepare();
                try {
                    BluetoothDiscoverer.findPrinters(getActivity(),
                            BTscannerDlg.this);
                } catch (ConnectionException e) {
                    // new
                    // UIHelper(BluetoothDiscovery.this).showErrorDialogOnGuiThread(e.getMessage());
                } finally {
                    Looper.myLooper().quit();
                }
            }
        }).start();
2) save the one selected
public void onItemClick(AdapterView parent, View view,
                    int position, long id) {
                DiscoveredPrinterBluetooth p = (DiscoveredPrinterBluetooth) devicesAdp
                        .getItem(position);
                PRINTER_ADDRESS = p.address;
    
If anyone needs more code to understand the problem, just ask for it.
Thank you very much for your help.
 
Enrico