Issues of state (was: Tkinter or wxpython?)

Cameron Laird claird at lairds.us
Wed Aug 8 22:23:45 CEST 2007


In article <7x8x8mpn37.fsf at ruckus.brouhaha.com>,
Paul Rubin  <http://phr.cx@NOSPAM.invalid> wrote:
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>I'm not sure what you're getting at in this context.  You can write a
>desktop app where the window system communicates with a gui toolkit
>through a socket (at least that's how X windows works), or you can
>write a web app where a browser communicates with an http listener
>through a socket.  What's the difference, as far as application state
>is concerned?  
>
>I haven't used wxpython but for tkinter you'd typically have a gui
>event loop in its own thread, communicating with the application
>through queues.  Similarly you can use BaseHTTPServer to collect
>browser hits and get the data out of them with the cgi module
>functions before passing them to the app.  If you want to handle
>multiple concurrent users you get into the usual issues of web
>servers, but if you're just doing a single user web implementation as
>an alternative to a desktop gui, some rudimentary locking is probably
>enough to stop accidental simultaneous connections.
>
>If the application is simple enough, you can just write it as a cgi
>and keep the state in disk files.

Others have answered this at other levels.  In elementary terms,
there truly is a difference, Paul, and one that's widely reified:
a "desktop client-server" application typically listens through
one socket, which therefore constitutes an index of the connection
or client, while a Web application communicates through a sequence
of independent HTTP transactions.  The latter can manage state only
to the extent it passes session information around.

As you correctly point out, there certainly are plenty of Web appli-
cations which cheerfully *do* pass session information.  As common
as it is, though--and I'm *still* writing CGI on occasion, a decade
after I was convinced it was a dead technique--it's not automatic.
HTTP is a stateless protocol, and therefore state management must
remain an issue.



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