OO design and multiple local sockets

[Andrew Bennetts]

On Fri, Jan 31, 2003 at 01:36:12AM +1300, Andrew McGregor wrote:
> I've got an awful case of writer's block on this one :-(
> 
> Problem:  I'm writing an app (an implementation of HIP, see 
> www.hip4inter.net) that uses raw sockets in a big way.  It needs to bind 
> local sockets to each IP address on the system so it can transmit packets 
> with each source address.  It also needs to know which address packets were 
> received on, and from where.  So far, so good.  It's threaded (pretty much 
> necessarily).  There are two pools of sockets for two different protocols 
> that have to interact.
> 
> Just the code for the protocol transforms and state machines is about 7k 
> lines, including tests, and works, but with only a single unbound local 
> socket, so some features I can't do yet.
> 
> What I can't figure out is what a clean OO design for the socket handling 
> looks like, managing the various queues and worker threads without getting 
> really hairy.  Can anyone help?

For OO design inspiration for socket programming, I suggest looking at
Twisted <http://twistedmatrix.com/> -- although admittedly it is rather
different to your design (being single-threaded asynchronous rather than
multi-threaded).  In particular its Factory and Protocol classes may be of
interest.

In fact, I'd really tempted to use Twisted for this -- have you looked at
it?  I've found it excels for writing servers that involve multiple
protocols.

(Not that being a developer of Twisted makes me biased or anything...)

-Andrew.