[Twisted-Python] socket communications in flash

[Bob Ippolito]

On Thursday, Jun 12, 2003, at 20:00 America/New_York, e okyere wrote:
> I am looking at doing low-level sock comms with flash mx and hopefully  
> c++
> and upon hitting this thread:
>
> http://twistedmatrix.com/pipermail/twisted-python/2002-May/001121.html
>
> thought I should contact you to see if you have any experience in that  
> line.
> If so, I'd appreciate any resources you can share or point to.

This is similar to how I've done it in the past (warning: untested, not  
commented, mostly rape & paste from other code I've written):

########
import sys, random, md5
from twisted.python.compat import True, False
from twisted.python import log
from twisted.protocols.basic import LineReceiver
from twisted.web import microdom
from twisted.internet.protocol import Factory


class XMLPipe(LineReceiver):
     delimiter = '\0'

     def connectionMade(self):
         pass

     def sendMessage(self, message):
         self.transport.writeSequence(('<packet>', str(message),  
'</packet>', self.delimiter))

     def lineReceived(self, line):
         if not line:
             log.msg("WARNING:  Empty message from client")
             return
         packet = microdom.parseString(line).childNodes[0]
         if packet.nodeName != 'packet':
             raise ValueError, '%r is not a packet tag' % packet
         self.packetReceived(packet)

     def packetReceived(self, packet):
         raise NotImplementedError

     def connectionLost(self, reason):
         pass

class FlashPipe(XMLPipe):
     def connectionMade(self):
         self.authenticated = False
         self.user = None
         self.issueChallenge()

     def packetReceived(self, packet):
         for node in packet.childNodes:
             self.nodeReceived(node)

     def nodeReceived(self, node):
         return getattr(self, 'handle_'+node.nodeName,  
self.xmlerror)(node)

     def xmlerror(self, node):
         log.msg('Unrecognized Node %r %r' % (node, node.toxml()))
         self.sendMessage('<error>Unrecognized Node</error>')

     def issueChallenge(self):
         # some entropy
         self.pendingChallenge = md5.new(''.join((
             hex(id(self)),
             hex(random.randrange(sys.maxint)),
         ))).hexdigest()
         self.sendMessage(''.join(
             ('<challenge>', self.pendingChallenge, '</challenge>'
         )))

     def handle_response(self, node):
         resp = node.firstChild().nodeValue.strip()
         for possible, user in self.factory.authorized.iteritems():
             h = md5.new(self.pendingChallenge)
             h.update(possible)
             if h.hexdigest() == resp:
                 break
         else:
             return
         log.msg('authenticated as %s' % user)
         self.user = user
         self.authenticated = True
         self.sendMessage('<authenticated />')

class FlashXMLFactory(Factory):
     noisy = 0
     protocol = FlashPipe
     authorized = {'somerandomdata' : 'valid user'}

if __name__=='__main__':
     from twisted.internet import reactor
     log.startLogging(sys.stdout)
     reactor.listenTCP(8888, FlashXMLFactory())
     reactor.run()

####

A conversation would look like this:
SERVER:  
'<packet><challenge>d41d8cd98f00b204e9800998ecf8427e</challenge></ 
packet>\0'
CLIENT:  
'<packet><response>f87504a987151d223335f0753f010b74</response></ 
packet>\0'
SERVER: '<packet><authenticated /></packet>\0'

-bob