[Twisted-Python] XWT

[Itamar Shtull-Trauring]

Hi,

I discovered XWT yesterday, and *wow*. This is very similar to something 
I've wanted to do, and it's very very cool.

Now, the thing is, my vision was slightly different - XWT seems to use the 
web model (XML-RPC and SOAP), where you send a request and get a reply, but 
there's no way for server to send data to client. A browser is of course 
limited to this because of HTTP, but in this case you don't need to limit 
yourself.

Why is this a limitation? Consider a chat application. In the XML-RPC model, 
you would need to continously poll the server for new messages - and if you 
want low latency, you need to send even more requests per second. This is 
very inefficent and puts a large load on the server.

What I was thinking of therefore was to use a protocol that is two-way, 
allowing the server to send commands to the client asynchronously. These 
would basically be GUI events just as you would from, say, Javascript. For 
example, in a chat application, a new message would result in the server 
sending a "add new text to message display wdiget" command being sent to the 
client, without the client having to request it.

In addition for event driven client-server applications, using such a 
protocol would also allow building P2P apps that use XWT.

My protocol of choice would be PB, which is a remote object protocol 
developed for the Twisted server framework 
(http://www.twistedmatrix.com/products/spread). It has implementation in 
Python, and a Java implementation I wrote 
(http://itamarst.org/software/TwistedJava-0.5.tar.gz). PB is very efficient, 
asynchronous, and two-way (for example, encoding an array containing a short 
string and two integers will take 150 bytes in XML-RPC, and 20 in PB). It 
was designed for chat systems, massive multiplayer games and other systems 
where latency must be kept at a minimum.

Given the time I would build such a system - a two-way version of XWT - 
using Twisted as a server and PB as the protocol. I don't really have the 
time for this right now :) However, some day I probably will, and it'd be 
great if I could reuse the XWT code, since most of the code for what I'm 
envisioning is basically identical.

I would therefore be very grateful if your design kept such a future 
requirement in mind. I'd be even happier if you'd decide to support PB as 
well, but I'd guess that's less likely to happen ;)

Anyway - great work!