I can't stop my program using LazWebsockets
lazarus / 38-Networking and Web Programming

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BlueIcaro · 2023-12-15 11:02

Hello, I'm trying to make a websocket client using
https://github.com/Warfley/LazWebsockets. But I can't stop my program
I wrote:
Code: [Select]procedure TForm1.FormClose(Sender: TObject; var
CloseAction: TCloseAction);
begin

  try
    FCommunicator.StopReceiveMessageThread;
    begin
      while FCommunicator.ReceiveMessageThreadRunning do //never
leaves this loop
      begin
        Application.ProcessMessages;
        Sleep(500);
        Application.ProcessMessages;
        FCommunicator.Close(True);
      end;
    end;
  finally
    FreeAndNil(FCommunicator);
    CloseAction := caFree;
  end;
end; 

But FCommunicator never stops receving messages.

What is happening?

I attach the project

Thanks in advance

/BlueIcaro

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Graham1 · 2023-12-16 04:10

I downloaded your project and tried it. I discovered you have fixed my
problem
(https://forum.lazarus.freepascal.org/index.php/topic,65537.0.html)
with Access Violation errors as your websocketclient.pas and
wsstream.pas files are different to the current Master version on
Github.

But now I also have the same problem as you. It looks like the
ThreadRunning status, as well as the FCommunicator.Open flag, isn't
getting updated so loops that check them never end. It's interesting
that if I comment out all the lines like

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i while
FCommunicator.xxxxx do sleep(nnn)
then everything seems to work fine. It doesn't seem like a very safe
solution though, so hopefully somebody else will find something.

But I have also found another problem. If the IP address is set to one
that doesn't exist then the Connect command waits for a long time,
during which the program says 'Not responding', before finally coming
back with a connection failed message. I use the code:

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i    try    
FCommunicator := Client.Connect(TSocketHandler.Create);   except     
Memo1.Lines.Add('Connect failed');      exit;   end; 
but it would be good to find out where the delay is happening and
either reduce the timeout or add an Application.ProcessMessages.

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Warfley · 2023-12-18 12:54

As this is my library, I'll take a look at it, but sadly I won't have
time for the rest of the year.

Please create a GitHub issue and I'll try to fix it as soon as
possible

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BlueIcaro · 2023-12-21 10:55

Hello @Graham1, I didn't modify that files, Only I downloaded the last
version from github.
@Warfley I'm going to open a issue.

Thanks
/BlueIcaro

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Warfley · 2023-12-21 15:38

As I said I do not have time to look at it, but if I remember
correctly this may be a known problem that the receiver thread only
check if it was halted between messages, so it will always wait for
one more message. So try if the thread is actually continuing for more
than one message.

A simple workaround should be to send a ping message after the stop,
as it should be answered with a pong, which results in the thread
checking the stopped flag again and terminating afterwards.

Need to fix that in the future by adding a timeout