Comments on: Code sample – socket client based on Twisted with PyQt

By: eliben

eliben — Sun, 24 Mar 2013 21:39:50 +0000

@Scott,

Thanks for your feedback. Unfortunately, I no longer have the setup to run this sample – so I won’t be able to help here. But yes, qt4reactor interaction is a tricky thing, IIRC, and it wasn’t easy to find a well-functioning implementation.

By: Scott

Scott — Sun, 24 Mar 2013 19:28:19 +0000

As a followup if you press the ‘Do It’ button then press the window close X button the application does exit to command line. So it appears that is you try or actually connect to backend server the application will exit when pressing the window close X button. It looks like you must do a connect and/or send to server to get everything to close and exit application.

By: Scott

Scott — Sun, 24 Mar 2013 19:19:09 +0000

There is an issue with this application as posted. If you run the application and never hit the “Do It” button but press the window close X the application does not close. I am currently developing an application and I have the same issue.

If you Cntrl-C the application after pressing the X on the window bar you get the following:
QObject::killTimers: timers cannot be stopped from another thread
and application does not exit. Still in a loop somewhere.

Where is a PyQt4 reactor that works? Meaning you can exit your Qt application. The posted sample above does not allow a close either. I have tried to add a stop method to reactor as well but application will not cleanly exiit.

I am using the PyQt 4.9.4 which is latest for binary installer. Also using Qt 4.8.1. Some incompatibility with qt4reactor. I have tried launchpad.net version of qt4reactor and can not get Qt QMainWindow to close.

By: Johanna

Johanna — Mon, 11 Jul 2011 08:42:42 +0000

Thanks for your response.

About the 64bits issue, I think I’ll just try to run something and ask questions on the mailing list. But it’s not possible to install a 32-Python (not my machine, not my choice..)

I guess I was just wondering if it was easy to convert something and not start from scratch. But you’re right, I’ll try to get going and see how it turns out !

By: eliben

eliben — Fri, 08 Jul 2011 17:48:59 +0000

Johanna,

Your question is too general. How simple it is to convert an application to Twisted, depends on the application, of course, what would you expect ? I suggest you just get going, and if you run into specific problems, ask questions in the Twisted mailing list or on Stack Overflow. I confess I don’t have much experience with Twisted.

Re 64-bit Windows, I have no idea. You can always install a 32-bit Python on a Win 64 machine, so Twisted surely can run there. Don’t know about 64-bit Python.

By: Johanna

Johanna — Fri, 08 Jul 2011 15:46:36 +0000

Hi,
I am writing a PyQt application which I would like to turn into a client-server app (thiswas not planned at the beginning of the developement). I nerver used Twisted, and in a general way I suck at networking programming. So I guess my question is : is it simple to convert zn existing application to network app using Twisted ? Do you have any good advice apart from your post (which seems to be a good strating point) ?

Oh, and I am running under Windows 64bits, is it a problem for installing Twisted ?

By: Jean-Yves

Jean-Yves — Thu, 16 Jun 2011 07:35:05 +0000

Thanks for this solution using twisted and QT

By: Inmake

Inmake — Tue, 07 Jun 2011 12:52:19 +0000

А мне понравилось!

By: eliben

eliben — Fri, 27 May 2011 03:21:53 +0000

glyph

Thank you for the effort invested in Twisted! It’s good to hear about making qt4reactor official.

Regarding Int32StringReceiver, I definitely saw it, but it’s big-endian (network order) 32-bit integer, while I use a little-endian prefix. Not that I have any particular preference for little-endian, but I just wanted to keep the protocol the same as in the previous sample.

I will read about endpoints, thanks.

By: Glyph

Glyph — Thu, 26 May 2011 15:49:38 +0000

Thanks for posting a Twisted solution to your GUI networking problem!

A few minor notes:

With the advent of PySide, we may be able to address those licensing issues and have an officially-supported qt reactor again.

You don’t need to set attributes on your own IntNStringReceiver to get “little-endian 32-bit length prefix” behavior; that’s already in Twisted as Int32StringReceiver.

Finally, you can save a bit of code by using the ‘endpoints’ connection APIs, which will give you a Deferred that fires with your protocol instance when it’s connected rather than you needing to set up your own clientReady callback.