Crash when disabling tcp server while connected

[jeffrson]

What OS?

• [ X ] Windows
• Mac
• Linux (Which distro?)

Description of issue

I checked "Persistent TCP". When I disable TCP server by clicking the button (bottom TCP: port) while the seperate window with the persistent TCP connection is still open, PacketSender crashs.

[SurrealSky]

I also found this bug and tried to fix it. I hope the author can fix it as soon as possible.

[dannagle]

Yes, I was able to replicate this bug. It is being actively worked.

A fix didn't make it in to the release from a few days ago since what I need to do is pretty intense. For now, the workaround is to manually disconnect and close the pop-ups before disabling the server.

[bladerunner2020]

On Mac it also crashes.

[ProfessorTom]

@bladerunner2020 @jeffrson @SurrealSky Is this still an active bug?

[jeffrson]

Yes - however, now it (mostly, if not always) deadlocks. It crashes as soon as the client disconnects (*)

Windows 11, PacketSender 8.9.1

(*) my test client runs from Windows Terminal - disabling the TCP server in PacketSender blocks the entire terminal. I have to kill the terminal process, even if the test client had been killed before. The terminal can be accessed again, if I kill PacketSender instead (all applications running locally).

[ProfessorTom]

@jeffrson Do you know QT or C++?

I tried to vibe-code a Connection Manager. While doing this work, I combined an rm command with the build command and I wiped out an hour's work. Consequently, I had to start from an in progress state via a Time Machine backup.

Here's my WIP branch

I'm not saying it's right or it's production ready.

After I got to this point, I realized that the windows will still send packets even when the address scheme is wrong e.g. would send to IPV4 addresses when the main window had been toggled to IPV6. I tried fixing the last night and just went round and round in circles. Have a bunch of nasty, uncommitted, code that doesn't behave right on my machine.

Perhaps if I had some time to talk with @dannagle or got some guidance here, I could get a solution over the line.

Thoughts?

[bladerunner2020]

@bladerunner2020 @jeffrson @SurrealSky Is this still an active bug?

PS v8.8.9, MacOS Apple Silicon 26.3 - the issue is still here.

[dannagle]

The problem is the hand-off of the socket to the new window. That is the wrong way to do it. You can blame me 10 years ago when I wrote it not quite understanding what I was doing. I thought it would be faster, which it was not, and I made an architectural problem.

The correct approach is to have the socket managed entirely by the main window and just create a data connection to/from the persistent window. That way, when the TCP (or any server) is closed, that simple data connection is severed and not an orphaned thread.

[ProfessorTom]

@dannagle I don't want to blame anyone, I just want to fix this correctly.

I've got a PR up (#412 ) that adds unit tests to the project. Once you merge that in, my next task will be to unit test other low hanging fruit along the path to a fully tested connection manger.

There may be some side issues with creating more than one server and the servers not being terminated, but I'm not entirely sure.

C++ isn't my strong suit and prior to working on this project I had never worked with Qt before. I think I'm starting to understand the current architecture, I just need more time to play with it.

Just like with the OS toggling between light and dark modes, I really want to solve this problem. Currently, I'm a bit out over my skies, but I feel this is within my ability given a bit more grind.

[ProfessorTom]

I'm going to try implementing this (or something very similar) with unit tests:

   └── owns PacketNetwork (existing)
          └── owns ConnectionManager (new / renamed & upgraded)
                 └── owns std::vector<std::unique_ptr<Connection>>   // or QMap<quint64, std::unique_ptr<Connection>>
                         └── each Connection (RAII wrapper)
                                 ├── owns TCPThread* or Worker + QTcpSocket*
                                 ├── owns the socket
                                 └── emits dataReceived, stateChanged, error, etc.

[ProfessorTom]

WIP: https://github.com/ProfessorTom/PacketSender/tree/tomas/connection-raii-initial