"Chris Angelico" <ros...@gmail.com> wrote in message
news:CAPTjJmoWaHPZk=DAxbfJ=9ez2aj=4yf2c8wmbryof5vgn6e...@mail.gmail.com...
> On Thu, Apr 10, 2014 at 7:17 PM, Frank Millman <fr...@chagford.com> wrote:
>> The current version of my program uses HTTP. As I understand it, a client
>> makes a connection and submits a request. The server processes the
>> request
>> and returns a result. The connection is then closed.
>>
>> In this scenario, does async apply at all? There is no open connection to
>> 'select' or 'poll'. You have to ensure that the request handler does not
>> block the entire process, so that the main loop is ready to accept more
>> connections. But passing the request to a thread for handling seems an
>> effective solution.
>
[...]
Thanks, Chris - I am learning a lot!
I have skipped the first part of your reply, as it seems to refer to the
client. I am using a web browser as a client, so I don't have to worry about
programming that.
>
> When you write the server, you effectively have the same principle,
> with one additional feature: a listening socket becomes readable
> whenever someone connects. So you can select() on that socket, just
> like you can with the others, and whenever there's a new connection,
> you add it to the collection and listen for requests on all of them.
> It's basically the same concept; as soon as you can accept a new
> connection, you do so, and then go back to the main loop.
>
This is where it gets interesting. At present I am using cherrypy as a
server, and I have not checked its internals. However, in the past I have
dabbled with writing server programs like this -
while self.running:
try:
conn,addr = self.s.accept()
Session(args=(self, conn)).start()
except KeyboardInterrupt:
self.shutdown()
In this scenario, the loop blocks on 'accept'.
You seem to be suggesting that I set the socket to 'non-blocking', use
select() to determine when a client is trying to connect, and then call
'accept' on it to create a new connection.
If so, I understand your point. The main loop changes from 'blocking' to
'non-blocking', which frees it up to perform all kinds of other tasks as
well. It is no longer just a 'web server', but becomes an 'all-purpose
server'.
Much food for thought!
Frank
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