How to define a callback function to receive TCP/IP data stream in MATLAB GUI?

I wrote the following simple GUI to do that but still the callback function does not run at all

function com_test_OpeningFcn(hObject, eventdata, handles, varargin)
% This function has no output args, see OutputFcn.
% hObject    handle to figure
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)
% varargin   command line arguments to com_test (see VARARGIN)
handles.t_rzm = tcpip('169.254.181.51', 51000);
set(handles.t_rzm,'ByteOrder','littleEndian');

fopen(handles.t_rzm);
handles.t_rzm.BytesAvailableFcn = @RXDATA;
% Choose default command line output for com_test
handles.output = hObject;
% the remote computer is sending the data
% Update handles structure
guidata(hObject, handles);

function RXDATA(hObject, eventdata, handles) % The callback function supposed to get data
% handles = guidata(hObject);
disp('yes')
dum_PB_Callback(handles.dum_PB,event,dat)

guidata(handles.dum_PB,handles) %%function ends
guidata(hObject, handles);

I also defined a dummy push button to trigger the RXDATA function but it does not help.

% --- Executes on button press in dum_PB. (Dummy Push Button)
function dum_PB_Callback(hObject, eventdata, handles)
% hObject    handle to dum_PB (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)
disp('dum_PB_Callback')
% if handles.UserData.sync==1
handles.t_rzm.BytesAvailableFcn = @RXDATA;
% end
guidata(hObject,handles) %%dummy button function ends