Loop only the first execution

Hello,

I am trying to create a loop in a GUI that only loops the first time the program is run through, and then skip that portion any other time it comes to it. How can I do this?

This is the code I need in the loop to execute only the first time:

connection = tcpip('127.0.0.1', 3333, 'NetworkRole', 'server'); % connect to server socket via TCP/IP

fclose(connection);%Make sure socket is closed before attempting to open port

fopen(connection);

Thanks in advance for any help!

SM

Answer 1

[Walter Roberson]

persistent has_been_initialized

if isempty(has_been_initialized)
  connection = tcpip('127.0.0.1', 3333, 'NetworkRole', 'server'); % connect to server socket via TCP/IP
  fclose(connection);%Make sure socket is closed before attempting to open port
  fopen(connection);
  has_been_initialized = true;
end

Reminder: your variable connection looks like a local variable in the workspace of that function. If that local variable goes out of scope then the connection will be shut down.

http://matlab.wikia.com/wiki/FAQ#How_can_I_share_data_between_callback_functions_in_my_GUI.28s.29.3F

[Me29]

Ok. I am using this in a GUI. I don't want it to close when it goes out of that function. How can I setup connection outside of the function but still be in the GUI? I tried making it global inside the GUI and it crashed my program. Basically I want to connect and loop while connected, and do some tcpread/write while looping, depending on which button is pressed. How can I do that?

Thanks for the help,

SM

[Walter Roberson]

See the above link on the various ways you can export information from a function.

One way would just be

persistent connection
if isempty(connection)
  connection = tcpip('127.0.0.1', 3333, 'NetworkRole', 'server'); % connect to server socket via TCP/IP
  fclose(connection);%Make sure socket is closed before attempting to open port
  fopen(connection);
end