Why does not this program code work in the third TCP communication?

I create TCP server that can communicate many times. But, following code cannot work my target.Best Regars. I make SERVER.m and CLIENT.m. Further, I run each file by two matlab on same PC.

% SERVER
clear all
clc
disp('Server Stated');
server = tcpip('0.0.0.0', 30000, 'NetworkRole', 'server');
while true
  disp('waiting for connection');
  fopen(server);
  disp('Connection OK');
  data = fread(server, server.BytesAvailable);
  disp('read data');
  disp(char(data));
  fclose(server);
  disp('end connection');
end
% Client
clear all
clc
data = 'H';
disp('client Stated');
client = tcpip('localhost', 30000, 'NetworkRole', 'client');
disp('waiting for connection');
fopen(client);
disp('Connection OK');
fwrite(client, data);
disp('write data');
fclose(client);

[Greg]

Are you seeing any of the disp output from the Client after the Server is started?

Answer 1

[Greg]

Take the fopen and fclose out of the while loop. Repeatedly opening and closing the tcpip obj is unnecessary, and usually extremely costly (performance). Further, since there is no wait time for the client to send a message between the open and close, you have practically 0 chance of catching the message.

[Naoya Inoue]

Is Your Idea Fllowing Code ?

 disp('waiting for connection');
 fopen(server);
 while true
   disp('Connection OK');
   data = fread(server, server.BytesAvailable);
   disp('read data');
   disp(char(data));
 end
 fclose(server);
 disp('end connection');

disp error message on Server Command window.

ERROR: icinterface/fread (line 160)
 SIZE must be greater than 0.
 ERROR: matlab_server_ex (line 27)
  data = fread(server, server.BytesAvailable);

[Greg]

Now you need some logic to prevent reading if there are no bytes available.