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  1. Hello Community, since last week I have been trying to let a TsslWSocket and a TsslWSocketServer communicate with each other. I want to get a long-term stable connection between a TCP client and a TCP server that is secured with TLS1.3. However, after a runtime of a few minutes, the data transfer breaks down. There is a client thread and a server thread. In the respective Execute method I create the socket and initialize it, call Listen (server) or Connect (client) and run the MessageLoop. After a successful SSL handshake, my client sends 128KB data packets to the server. The data arrives at the server, TwSocketClient.onDataAvailable is triggered, the bytes can be read there with TwSocketClient (Sender).Receive (pBuffer ...). When the server has received 128KB, it sends an "ACK" packet to the client (An AnsiString "ACK", 3 bytes). When the client receives the packet, it sends again 128KB of testdata. This works a few thousand, sometimes some tenthousands times, until TwSocketClient.onDataAvailable is suddenly no longer called. There is no OnSessionClosed, no onError, no onException and also no onBgException that would indicate a problem. Apparently the problem is on the client side: A running Wireshark shows an [ACK] packet from the server to the client as last entry. Further clicks on the "Manual Send" button do not lead to any further lines in the Wireshark log. When this state has been reached another client can connect to the server without any problems, so the server is not completely dead. I have no idea what I could do wrong ... Maybe it's not ok to send in the context of another thread? But how is that supposed to work when the client thread is blocked by the MessageLoop? Simultaneous web browsing leads to the problem faster. When I look at any website, it usually takes less than half a minute to see the problem. My test project is attached. I would be interested to know if you have observed the same problem and if anyone has a guess as to what might be the cause ... The project is complete, the Win32 folder also contains the certificate used for testing ... Usage: Enter your own IP address, press the "btCreateStart" button, then the "btSendData Manual Send" button. The "logICStest.log" file in the program directory grows until the problem occurs ... Thanks in advance... P.S: I have already tried not to send after receiving the ACK packet, but cyclically via timer or thread. If you can select both in the test project with checkboxes, the result is the same. The problem does not only occur with TLS1.3, also with TLS1.2. I even think it shows up without encryption, just takes longer ... I crossposted this in the german Delphi-Praxis in german language (https://www.delphipraxis.net/205223-stabile-tcp-verbindung-mit-ics-ich-kriegs-nicht-hin.html)... Test Overbyte ISC Client und Server.7z
  2. Using Delphi 10.3.2 I've encountered the following problem (specifically on Windows, not sure about other platforms): After using TParallel or TTask, not all threads in the thread pool return to idle as expected. I've prepared the following simple example: procedure TForm.Button1Click(Sender: TObject); var SW:TStopWatch; procedure Load; begin TParallel.For(0, 99999999, procedure(i: Integer) var T:Single; begin T:=Sin(i/PI); end); end; begin Memo1.Lines.Add('PPL Test ---------------'); Memo1.Lines.Add('Before: '+TThreadPoolStats.Current.Formatted); SW:=TStopWatch.StartNew; Load; Memo1.Lines.Add('Finished in '+SW.Elapsed.ToString); Memo1.Lines.Add('After: '+TThreadPoolStats.Current.Formatted); Memo1.Lines.Add('------------------------'); end; Repeatedly pressing the button results in the following output: PPL Test --------------- Before: 0 Worker Threads (56 .. 1400) / 0 Idle / 0 Retired / 0 Suspended / Avg. CPU = 0 / Curr. CPU = 0 Finished in 00:00:09.8423686 After: 56 Worker Threads (56 .. 1400) / 43 Idle / 0 Retired / 0 Suspended / Avg. CPU = 30 / Curr. CPU = 100 ------------------------ PPL Test --------------- Before: 56 Worker Threads (56 .. 1400) / 43 Idle / 0 Retired / 0 Suspended / Avg. CPU = 36 / Curr. CPU = 0 Finished in 00:00:04.7841342 After: 65 Worker Threads (56 .. 1400) / 50 Idle / 0 Retired / 0 Suspended / Avg. CPU = 43 / Curr. CPU = 50 ------------------------ PPL Test --------------- Before: 65 Worker Threads (56 .. 1400) / 50 Idle / 0 Retired / 0 Suspended / Avg. CPU = 42 / Curr. CPU = 0 Finished in 00:00:04.7090980 After: 74 Worker Threads (56 .. 1400) / 55 Idle / 0 Retired / 0 Suspended / Avg. CPU = 42 / Curr. CPU = 48 ------------------------ PPL Test --------------- Before: 74 Worker Threads (56 .. 1400) / 55 Idle / 0 Retired / 0 Suspended / Avg. CPU = 38 / Curr. CPU = 0 Finished in 00:00:02.3904253 After: 74 Worker Threads (56 .. 1400) / 50 Idle / 0 Retired / 0 Suspended / Avg. CPU = 57 / Curr. CPU = 98 ------------------------ PPL Test --------------- Before: 74 Worker Threads (56 .. 1400) / 50 Idle / 0 Retired / 0 Suspended / Avg. CPU = 51 / Curr. CPU = 0 Finished in 00:00:05.2865123 After: 84 Worker Threads (56 .. 1400) / 55 Idle / 0 Retired / 0 Suspended / Avg. CPU = 44 / Curr. CPU = 41 ------------------------ PPL Test --------------- Before: 84 Worker Threads (56 .. 1400) / 55 Idle / 0 Retired / 0 Suspended / Avg. CPU = 36 / Curr. CPU = 0 Finished in 00:00:06.8032435 After: 96 Worker Threads (56 .. 1400) / 64 Idle / 0 Retired / 0 Suspended / Avg. CPU = 36 / Curr. CPU = 32 ------------------------ PPL Test --------------- Before: 96 Worker Threads (56 .. 1400) / 64 Idle / 0 Retired / 0 Suspended / Avg. CPU = 0 / Curr. CPU = 0 Finished in 00:00:07.7921758 After: 111 Worker Threads (56 .. 1400) / 77 Idle / 0 Retired / 0 Suspended / Avg. CPU = 27 / Curr. CPU = 23 ------------------------ PPL Test --------------- Before: 111 Worker Threads (56 .. 1400) / 77 Idle / 0 Retired / 0 Suspended / Avg. CPU = 20 / Curr. CPU = 0 Finished in 00:00:02.3559000 After: 111 Worker Threads (56 .. 1400) / 77 Idle / 0 Retired / 0 Suspended / Avg. CPU = 48 / Curr. CPU = 100 ------------------------ PPL Test --------------- Before: 111 Worker Threads (56 .. 1400) / 77 Idle / 0 Retired / 0 Suspended / Avg. CPU = 48 / Curr. CPU = 0 Finished in 00:00:06.6491982 After: 122 Worker Threads (56 .. 1400) / 87 Idle / 0 Retired / 0 Suspended / Avg. CPU = 33 / Curr. CPU = 100 ------------------------ Even after the first run, only 43 threads in the pool seem to have returned to idle. Instead, with almost every further run, the total number of worker threads is increased to make up the difference. Despite this, the total CPU usage is going down slowly. If I wait for the inactive threads to be automatically retired and run the test again, I get something like this: PPL Test --------------- Before: 0 Worker Threads (56 .. 1400) / -36 Idle / 0 Retired / 0 Suspended / Avg. CPU = 0 / Curr. CPU = 0 Finished in 00:00:09.5530676 After: 56 Worker Threads (56 .. 1400) / 20 Idle / 0 Retired / 0 Suspended / Avg. CPU = 30 / Curr. CPU = 100 ------------------------ A negative number of idle threads? And after the run, only 20 threads are stated as idle again. Further runs result in the behavior described above. If someone could shed some light on all this for me, I would highly appreciate it! Am I doing something wrong here? What do I need to do to get 100% CPU usage on every run, without the thread pool ballooning? Thanks!
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