[Twisted-Python] How to dispatch message to different servers

[Laurens Van Houtven]

Ah, but that too appears to be missing in the original code ;-)

The stuff you're doing with deferreds there seems a bit strange. In your
example, why not just call sendMessage when you get the packet?


On Sat, Mar 2, 2013 at 2:28 PM, Benjamin BERTRAND <beenje at gmail.com> wrote:

>
> Le 2 mars 2013 à 10:08, Laurens Van Houtven <_ at lvh.cc> a écrit :
>
> Yes, that looks okay, but that wasn't in your original sample ;-)
>
>
> Yep, sorry about that.
> I was more focused on the ServerFactory and Protocol.
> The pcap in a thread comes from the link I mentioned in my first post:
> http://dound.com/2009/09/integrating-twisted-with-a-pcap-based-python-packet-sniffer/
> But I know, it's better to put everything in one post. People shouldn't
> have to click links.
>
> I'm on my phone at the moment which isn't great for code review, but it
> looks like you only fire one deferred per line?
>
>
> There is a specific deferred by line.
> I re-arm it in the messageToSend method (that wasn't in the sample either).
> In the Oldimon class, I have:
>
>     def messageToSend(self, message):
>         self.sendMessage(message)
>         # Re-arm the deferred
>         self.factory.deferred[self.line] = defer.Deferred()
>         self.factory.deferred[self.line].addCallback(self.messageToSend)
>
>
> On Mar 2, 2013 9:50 AM, "Benjamin BERTRAND" <beenje at gmail.com> wrote:
>
>>
>> Le 2 mars 2013 à 04:34, exarkun at twistedmatrix.com a écrit :
>>
>> > On 1 Mar, 09:52 pm, beenje at gmail.com wrote:
>> >> Thanks for the answer!
>> >>
>> >> I was hoping to avoid having to put something like AMP in place,
>> >> because it looked a bit overkill for my case.
>> >> I think I actually found a way :-)
>> >
>> > Unfortunately, it looks like the code that you shared will only work
>> > accidentally (if at all).  You cannot use Twisted APIs except in the
>> > reactor thread.  You will at least need to add in some code to send data
>> > back to the reactor thread before you use Twisted APIs (such as
>> > `Deferred.callback`).
>>
>>
>> In run_pcap, I call reactor.callFromThread(callback, x25_data, line_id).
>> See below.
>> That seems to work with the tests I did.
>> Am I missing something?
>>
>> /Benjamin
>>
>> def run_pcap(device, pcap_filter, callback):
>>
>>     def analyse_packet(hdr, data):
>>         # check the data
>>         reactor.callFromThread(callback, x25_data, line_id)
>>
>>     p = pcapy.open_live(device, 65535, 1, 100)
>>     p.setfilter(pcap_filter)
>>     p.loop(-1, analyse_packet)
>>
>>
>> class Oldimon(Protocol):
>>
>>     def __init__(self, factory):
>>         self.factory = factory
>>         self.line = None
>>
>>     def connectionMade(self):
>>         # Check the server port to get the line
>>         # associated to this protocol
>>         port = self.transport.getHost().port
>>         self.line = LINES_PORT[port]
>>         # Add the callback for this line
>>         self.factory.deferred[self.line] = defer.Deferred()
>>         self.factory.deferred[self.line].addCallback(self.messageToSend)
>>
>>
>> class OldimonFactory(ServerFactory):
>>
>>     def __init__(self, device, pcap_filter):
>>         # pcapDataReceived callback is called everytime a message
>>         # is received
>>         reactor.callInThread(run_pcap, device, pcap_filter,
>> self.pcapDataReceived)
>>         # Dict with a deferred for each line
>>         self.deferred = dict(zip(LINES_PORT.values(), [None] *
>> len(LINES_PORT)))
>>
>>     def buildProtocol(self, addr):
>>         return Oldimon(self)
>>
>>     def pcapDataReceived(self, data, line):
>>         if self.deferred[line] is not None:
>>             # Fire the callback for line
>>             d, self.deferred[line] = self.deferred[line], None
>>             d.callback(data)
>>
>> oldimon_factory = OldimonFactory(device, pcap_filter)
>> for port in LINES_PORT.keys():
>>     reactor.listenTCP(port, oldimon_factory)
>> reactor.run()
>>
>>
>> >
>> > Jean-Paul
>> >
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-- 
cheers
lvh
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