Hi Andrew,
On 18 Apr 2008, at 01:32, Andrew McNabb wrote:
First, I think I understand the difference between protocol factories
and protocols, but I could use a little reassurance. My current
understanding is that the protocol factory holds the state that is
common to all connections, whereas the protocol holds the state
that is
specific to a particular connection. Is that an accurate
understanding?
No, this is not quite correct. In the case of a
ServerProtocolFactory, you are right, there is one instance for your
server, but it isn't responsible for managing state. New connections
to your server will cause the reactor to call buildProtocol in your
ServerFactory. This, in turn, will create one instance of your
ServerProtocol for each new connection. It is the ServerProtocol that
manages the state of that single connection. If you want to manage
some kind of global state between connections, you should write a
logic class that exists as a single, global instance within your
application.
If that is correct, then what is the difference between a protocol
factory and a protocol for a client (like HTTPClient) where only one
connection is involved? I'm a bit confused about why
HTTPClientFactory
isn't a trivial class. According to my current understanding, all of
the logic would be in HTTPClient.
A ClientProtocolFactory instance is created for *every* client
connection you attempt to create. The point here is that your
ClientProtocol is not instantiated *until* the connection has been
made to your remote resource. The ClientProtocolFactory manages the
instantiation of your ClientProtocol when successfully connected. I
agree that 'ClientProtocolFactory' is somewhat misleading as it
indicates that it is possible to create more than one ClientProtocol
from your factory. Within normal design patterns, this would be true,
but in this case your ClientProtocolFactory will only ever create one
instance of your ClientProtocol (unless you are doing something
*really* funky - and probably bad!).
To sum up, you always create a new ClientProtocolFactory when making
a new client connection:
reactor.connectTCP(host, port, ClientProtocolFactory()
Repeat for more clients...
Hope that helps,
Matt
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