add code to handle resending the notifys out every seven minutes..

This should prevent the DSM-520 from saying we've disappeared...

7 minutes means 4 sends before the 30 minutes max-age hits and is
a pretty good compromise, though we do send out five notifies each
time...

[git-p4: depot-paths = "//depot/": change = 1087]

SSDP.py

@@ -15,7 +15,7 @@ import string
 
 from twisted.python import log
 from twisted.internet.protocol import DatagramProtocol
-from twisted.internet import reactor
+from twisted.internet import reactor, task
 
 # TODO: Is there a better way of hooking the SSDPServer into a reactor
 # without having to know the default SSDP port and multicast address?
@@ -37,12 +37,22 @@ class SSDPServer(DatagramProtocol):
 	stdheaders = [ ('Server', 'Twisted, UPnP/1.0, python-upnp'), ]
 	elements = {}
 	known = {}
+	tasks = []
 
 	def doStop(self):
 		'''Make sure we send out the byebye notifications.'''
 
-		for st in self.known:
+		while True:
+			try:
+				t = self.tasks.pop()
+				t.stop()
+			except IndexError:
+				break
+
+		for st in self.known.keys():
 			self.doByebye(st)
+			del self.known[st]
+
 		DatagramProtocol.doStop(self)
 
 	def datagramReceived(self, data, (host, port)):
@@ -113,6 +123,10 @@ class SSDPServer(DatagramProtocol):
 		self.known[st]['CACHE-CONTROL'] = 'max-age=1800'
 		self.doNotify(st)
 
+		t = task.LoopingCall(lambda: self.doNotify(st))
+		t.start(7 * 60)
+		self.tasks.append(t)
+
 	def doByebye(self, st):
 		"""Do byebye"""