Communicating between iOS and Android with Bluetooth LE

Question

I\'ve got a working app using CoreBluetooth to communicate between an iPad (central) and iPhone (peripheral). I have one service that has two characteristics. I have a Nexus

Answer 1

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:

@Override
public 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)
                }
            }
        }
    }
}