Error Sync Response from bluetooth

I want to capture some responses data after I send some data via bluetooth but I have a problem at the time of capture, I send "a" Into my bluetooth module and should send me a response to 1 or 0, just after sent, but there is an error on the part of the catch which sent the data and making me answer a previous response. example: Correct

App                            Bluetooth                             App
Send "a"          ===>         get "a"         must response 1 but   NULL
Send "b"          ===>         get "b"         must response 0 but   1   
Send "a"          ===>         get "a"         must response 1 but   0

var ilu1= Ti.UI.createButton({
    width : Ti.UI.FILL,
    height : '80dp',
    shadowColor: '#000',
    shadowOffset: {x:0, y:0},
    shadowRadius: 2,
    font:{
      fontSize:55,
      fontFamily: customFont2
    },
    textAlign : Titanium.UI.TEXT_ALIGNMENT_CENTER,
    verticalAlign : Titanium.UI.TEXT_VERTICAL_ALIGNMENT_BOTTOM,
    title : 'L',
    color : '#fff',
    backgroundColor:'#005a93',
    backgroundSelectedColor: '#1f2d46', 
    backgroundFocusedColor: '#1f2d46', 
    touchEnabled: true, 
    zIndex:2
});
ilu1.addEventListener('click', function() {
    novarumbluetooth.sendData('a');
    actualizalabel.text = 'Actualizando';
        var responsebtilu = novarumbluetooth.addEventListener('nb_onReceiveData', function(e)
        {          
           Ti.App.responsebt2 = e.data; 
        });
    alert(Ti.App.responsebt2);
    if (Ti.App.responsebt2=='1') {
        ilu1.title = 'K';
        actualizalabel.text = 'Actualizado';
    } else {
        actualizalabel.text = 'Error';
    };
 
})