Serial Port Close and Open

I have design in GUIDE

First, I Write and Read. It's OK!

Second, I Write and Read

=> Write is OK! (The Board has LCD display), But Read data is First Write Data or all zero

=>However, Serial Port Close and Open then Second Write data is Read

EXAMPLE

WRITE 2, READ 2

WRTE 3 READ 2 or '0'

PORT CLOSE AND OPEN, THEN READ IS 3

WHERE IS THE PROBLEM?

% ------- Serial Port Open ----------------

function portopen_Callback(hObject, eventdata, handles)

global s

global portnum

s = serial(portnum, 'BaudRate', 115200, 'DataBits', 8, 'StopBits', 1, 'Parity', 'non');

set(s,'Terminator','');

fopen(s);

set(handles.text6,'String',' 115200bps, Data:8, Stop:1, No Parity'); % Overwrite

set(handles.text5,'String', [portnum ' Connect :']); % Overwrite

% Update handles structure

guidata(hObject, handles);

% --- Executes on button press in portclose.

function portclose_Callback(hObject, eventdata, handles)

global s

set(handles.text5,'String', ' Disconnect');

set(handles.text6,'String','');

fclose(s);