Add support for MyListener call getting updates to service TXT record…

…s (2nd attempt) (#166)

Add support for MyListener call getting updates to service TXT records

At the moment, the implementation supports notification to the  ServiceListener class for additions and removals of service, but for service updates to the TXT record, the client must poll the ServiceInfo class. This draft PR provides a mechanism to have a callback on the ServiceListener class be invoked when the TXT record changes.

test_zeroconf.py

@@ -737,12 +737,13 @@ def test_integration_with_listener_class(self):
 
         service_added = Event()
         service_removed = Event()
+        service_updated = Event()
 
         subtype_name = "My special Subtype"
         type_ = "_http._tcp.local."
         subtype = subtype_name + "._sub." + type_
         name = "xxxyyyæøå"
-        registration_name = "%s.%s" % (name, type_)
+        registration_name = "%s.%s" % (name, subtype)
 
         class MyListener(r.ServiceListener):
             def add_service(self, zeroconf, type, name):
@@ -752,6 +753,16 @@ def add_service(self, zeroconf, type, name):
             def remove_service(self, zeroconf, type, name):
                 service_removed.set()
 
+        class MySubListener(r.ServiceListener):
+            def add_service(self, zeroconf, type, name):
+                pass
+
+            def remove_service(self, zeroconf, type, name):
+                pass
+
+            def update_service(self, zeroconf, type, name):
+                service_updated.set()
+
         listener = MyListener()
         zeroconf_browser = Zeroconf(interfaces=['127.0.0.1'])
         zeroconf_browser.add_service_listener(subtype, listener)
@@ -779,7 +790,7 @@ def remove_service(self, zeroconf, type, name):
             assert service_added.is_set()
 
             # short pause to allow multicast timers to expire
-            time.sleep(2)
+            time.sleep(3)
 
             # clear the answer cache to force query
             for record in zeroconf_browser.cache.entries():
@@ -799,9 +810,28 @@ def remove_service(self, zeroconf, type, name):
             assert info is not None
             assert info.properties[b'prop_none'] is False
 
+            # Begin material test addition
+            sublistener = MySubListener()
+            zeroconf_browser.add_service_listener(registration_name, sublistener)
+            properties['prop_blank'] = b'an updated string'
+            desc.update(properties)
+            info_service = ServiceInfo(
+                subtype, registration_name,
+                socket.inet_aton("10.0.1.2"), 80, 0, 0,
+                desc, "ash-2.local.")
+            zeroconf_registrar.update_service(info_service)
+            service_updated.wait(1)
+            assert service_updated.is_set()
+
+            info = zeroconf_browser.get_service_info(type_, registration_name)
+            assert info is not None
+            assert info.properties[b'prop_blank'] == properties['prop_blank']
+            # End material test addition
+
             zeroconf_registrar.unregister_service(info_service)
             service_removed.wait(1)
             assert service_removed.is_set()
+
         finally:
             zeroconf_registrar.close()
             zeroconf_browser.remove_service_listener(listener)

zeroconf.py

@@ -169,7 +169,7 @@ class InterfaceChoice(enum.Enum):
 class ServiceStateChange(enum.Enum):
     Added = 1
     Removed = 2
-
+    Updated = 3
 
 # utility functions
 
@@ -1267,6 +1267,9 @@ def add_service(self, zc, type_, name) -> None:
     def remove_service(self, zc, type_, name) -> None:
         raise NotImplementedError()
 
+    def update_service(self, zc, type_, name) -> None:
+        raise NotImplementedError()
+
 
 class ServiceBrowser(RecordUpdateListener, threading.Thread):
 
@@ -1312,6 +1315,9 @@ def on_change(zeroconf, service_type, name, state_change):
                     listener.add_service(*args)
                 elif state_change is ServiceStateChange.Removed:
                     listener.remove_service(*args)
+                elif state_change is ServiceStateChange.Updated:
+                    if hasattr(listener, 'update_service'):
+                        listener.update_service(*args)
                 else:
                     raise NotImplementedError(state_change)
             handlers.append(on_change)
@@ -1361,6 +1367,12 @@ def enqueue_callback(state_change: ServiceStateChange, name: str) -> None:
             if expires < self.next_time:
                 self.next_time = expires
 
+        elif record.type == _TYPE_TXT and record.name == self.type:
+            assert isinstance(record, DNSText)
+            expired = record.is_expired(now)
+            if not expired:
+                enqueue_callback(ServiceStateChange.Updated, record.name)
+
     def cancel(self):
         self.done = True
         self.zc.remove_listener(self)
@@ -1855,6 +1867,24 @@ def register_service(
             self.servicetypes[info.type] += 1
         else:
             self.servicetypes[info.type] = 1
+
+        self._broadcast_service(info)
+
+    def update_service(
+        self, info: ServiceInfo
+    ) -> None:
+        """Registers service information to the network with a default TTL.
+        Zeroconf will then respond to requests for information for that
+        service."""
+
+        assert self.services[info.name.lower()] is not None
+
+        self.services[info.name.lower()] = info
+
+        self._broadcast_service(info)
+
+    def _broadcast_service(self, info: ServiceInfo) -> None:
+
         now = current_time_millis()
         next_time = now
         i = 0
@@ -2031,9 +2061,12 @@ def handle_response(self, msg: DNSIncoming) -> None:
                         entry.reset_ttl(record)
             else:
                 self.cache.add(record)
+                if record.type == _TYPE_TXT:
+                    self.update_record(now, record)
 
         for record in msg.answers:
-            self.update_record(now, record)
+            if record.type != _TYPE_TXT:
+                self.update_record(now, record)
 
     def handle_query(self, msg: DNSIncoming, addr: str, port: int) -> None:
         """Deal with incoming query packets.  Provides a response if