I've already gone through this for at least one week having this same issue. I've already asked a question here and I've already answered on my own. The main problem is an Android BUG issue. It's sending a non permitted command on a fixed L2CAP channnel.

But when Android is communicating with normal peripheral BLE devices, it works pretty well. In fact, the BLE sample works like a charm. The problem is when is comunicating with an iOS device for example: Just after the connection is made, they start negotiating their connection parameters (this phase doesn't happen with normal BLE peripheral), and this is when the problem comes up. Android sends a bad command to iOS, iOS drops the connection. That's basically how it works

Some issues have been already reported to Google, and one of them have been already accepted and I hope they will start working on it soon.

Unfortunately, what you can do, is to wait until next Android release. Anyway, I highly suggest you to have a look at my issue report with all my test documents if you want to make some light on this problem.

Here's the link: https://code.google.com/p/android/issues/detail?id=58725

I've written a simple working example, well relatively simple, and included it open-source on Github: https://github.com/GitGarage. So far it has only been tested with an Android Nexus 9 and an iPhone 5s, but I presume it would also work with a Nexus 6 and various iPhone types. So far it is set up explicitly to communicate between one Android and one iPhone, but I presume it is tweakable to do much more.

Here are the key methods...

DROID SIDE - Sending to iOS:

private void sendMessage() {    Thread thread = new Thread(new Runnable() {        @Override        public void run() {            if (mBTAdapter == null) {                return;            }            if (mBTAdvertiser == null) {                mBTAdvertiser = mBTAdapter.getBluetoothLeAdvertiser();            }               // get the full message from the UI            String textMessage = mEditText.getText().toString();             if (textMessage.length() > 0)            {                   // add 'Android' as the user name                String message = "Android: " + textMessage;                 while (message.length() > 0) {                    String subMessage;                    if(message.length() > 8)                    {    // add dash to unfinished messages                        subMessage = message.substring(0,8) + "-";                         message = message.substring(8);                        for (int i = 0; i < 20; i++) // twenty times (better safe than sorry) send this part of the message. duplicate parts will be ignored                        {                            AdvertiseData ad = BleUtil.makeAdvertiseData(subMessage);                            mBTAdvertiser.startAdvertising(BleUtil.createAdvSettings(true, 100), ad, mAdvCallback);                            mBTAdvertiser.stopAdvertising(mAdvCallback);                        }                    }                    else                    {  // otherwise, send the last part                        subMessage = message;                        message = "";                        for (int i = 0; i < 5; i++)                        {                            AdvertiseData ad = BleUtil.makeAdvertiseData(subMessage);                            mBTAdvertiser.startAdvertising(                                    BleUtil.createAdvSettings(true, 40), ad,                                    mAdvCallback);                            mBTAdvertiser.stopAdvertising(mAdvCallback);                        }                    }                }                threadHandler.post(updateRunnable);            }        }    });    thread.start();}

DROID SIDE - Receiving from iOS:

@Overridepublic void onLeScan(final BluetoothDevice newDevice, final int newRssi,                     final byte[] newScanRecord) {    int startByte = 0;    String hex = asHex(newScanRecord).substring(0,29);       // check five times, startByte was used for something else before    while (startByte <= 5) {       // check if this is a repeat message        if (!Arrays.asList(used).contains(hex)) {            used[ui] = hex;            String message = new String(newScanRecord);            String firstChar = message.substring(5, 6);            Pattern pattern = Pattern.compile("[ a-zA-Z0-9~!@#$%^&*()_+{}|:\"<>?`\\-=;',\\./\\[\\]\\\\]", Pattern.DOTALL);               // if the message is comprised of standard characters...            Matcher matcher = pattern.matcher(firstChar);            if (firstChar.equals("L"))            {                firstChar = message.substring(6, 7);                pattern = Pattern.compile("[ a-zA-Z0-9~!@#$%^&*()_+{}|:\"<>?`\\-=;',\\./\\[\\]\\\\]", Pattern.DOTALL);                matcher = pattern.matcher(firstChar);            }            if(matcher.matches())            {                TextView textViewToChange = (TextView) findViewById(R.id.textView);                String oldText = textViewToChange.getText().toString();                int len = 0;                String subMessage = "";                   // add this portion to our final message                while (matcher.matches())                  {                    subMessage = message.substring(5, 6+len);                    matcher = pattern.matcher(message.substring(5+len, 6+len));                    len++;                }                subMessage = subMessage.substring(0,subMessage.length()-1);                Log.e("Address",newDevice.getAddress());                Log.e("Data",asHex(newScanRecord));                boolean enter = subMessage.length() == 16;                enter = enter && !subMessage.substring(15).equals("-");                enter = enter || subMessage.length() < 16;                textViewToChange.setText(oldText + subMessage.substring(0, subMessage.length() - 1) + (enter ? "\n" : ""));                ui = ui == 2 ? -1 : ui;                ui++;                Log.e("String", subMessage);            }            break;        }        startByte++;    }}

iOS SIDE - Sending to Android:

func startAdvertisingToPeripheral() {    var allTime:UInt64 = 0;    if (dataToSend != nil)    {        datastring = NSString(data:dataToSend, encoding:NSUTF8StringEncoding) as String        datastring = "iPhone: " + datastring        if (datastring.length > 15)        {            for (var i:Double = 0; i < Double(datastring.length)/15.000; i++)            {                let delay = i/10.000 * Double(NSEC_PER_SEC)                let time = dispatch_time(DISPATCH_TIME_NOW, Int64(delay))                allTime = time                dispatch_after(time, dispatch_get_main_queue(), { () -> Void in self.sendPart() });            }        }        else        {            var messageUUID = StringToUUID(datastring)            if !peripheralManager.isAdvertising {                peripheralManager.startAdvertising([CBAdvertisementDataServiceUUIDsKey: [CBUUID(string: messageUUID)]])            }        }    }}

iOS SIDE - Receiving from Android:

func centralManager(central: CBCentralManager!, didDiscoverPeripheral peripheral: CBPeripheral!, advertisementData: [NSObject : AnyObject]!, RSSI: NSNumber!) {    delegate?.didDiscoverPeripheral(peripheral)    var splitUp = split("\(advertisementData)") {$0 == "\n"}    if (splitUp.count > 1)    {        var chop = splitUp[1]        chop = chop[0...chop.length-2]        var chopSplit = split("\(chop)") {$0 == "\""}        if !(chopSplit.count > 1 && chopSplit[1] == "Device Information")        {            var hexString = chop[4...7] + chop[12...19] + chop[21...26]            var datas = hexString.dataFromHexadecimalString()            var string = NSString(data: datas!, encoding: NSUTF8StringEncoding) as String            if (!contains(usedList,string))            {                usedList.append(string)                if (string.length == 9 && string[string.length-1...string.length-1] == "-")                {                    finalString = finalString + string[0...string.length-2]                }                else                {                    lastString = finalString + string + "\n"                    println(lastString)                    finalString = ""                    usedList = newList                    usedList.append(string)                }            }        }    }}

I would like to add few information to this thread as a part of our RnD on BLE topic between cross platform.

Peripheral mode is working without any issues with Xiomi Mi A1 (OS version Oreo, Android 8.0).

Here are few observation on throughput that we found during our RnD on iPhone 8 and Xiomi Mi A1 but it still has to get matured with other custom Android OS used in latest Samsung S8. The below data is based on write_with_response.

1. iPhone 8 (BLE 5.0) as Central and Linux desktop (Ubuntu 16.04 with BLE dongle 4.0): MTU = 2048 : Throughput - 2.5 KiloBytes per sec.

2. iPhone 8 (BLE 5.0) as Central and Android OS with BLE version 4.2 as Peripheral(Xiomi Mi A1): MTU = 180 : Throughput - 2.5 KiloBytes per sec.

3. iPhone 8 (BLE 5.0) as Central and iPhone 7 plus (BLE 4.2) as Peripheral : MTU = 512 : Throughput - 7.1 KiloBytes per sec.

4. iPhone 8 (BLE 5.0) as Central and Samsung S8 (BLE 5.0) as Peripheral : Samsung S8 failed to work as peripheral

5. iPhone 8 (BLE 5.0) as Central and iPhone 8 plus (BLE 5.0) as Peripheral : MTU = 512 : Throughput - 15.5 KiloBytes per sec.