Implement ModifySubscriptionRequest_Encoding_DefaultBinary (#330)

* Added implementation for ModifySubscriptionRequest_Encoding_DefaultBinary, which is sent by some clients (Softing?) after a session has already been created and will kill the session if it's not implemented.

* Minor reshuffling of new code insertions. Added missing import.

Co-authored-by: Jonathan Cutting <jonathan.cutting@sartorius.com>

asyncua/server/internal_session.py

@@ -190,3 +190,6 @@ async def delete_monitored_items(self, params):
 
     def publish(self, acks: Optional[Iterable[ua.SubscriptionAcknowledgement]] = None):
         return self.subscription_service.publish(acks or [])
+
+    def modify_subscription(self, params, callback):
+        return self.subscription_service.modify_subscription(params, callback)

asyncua/server/subscription_service.py

@@ -7,6 +7,7 @@
 from typing import Dict, Iterable
 
 from asyncua import ua
+from asyncua.common import utils
 from .address_space import AddressSpace
 from .internal_subscription import InternalSubscription
 
@@ -41,6 +42,20 @@ async def create_subscription(self, params, callback=None, external=False):
         self.subscriptions[result.SubscriptionId] = internal_sub
         return result
 
+    def modify_subscription(self, params, callback):
+        # Requested params are ignored, result = params set during create_subscription.
+        self.logger.info("modify subscription with callback: %s", callback)
+        result = ua.ModifySubscriptionResult()
+        try:
+            sub = self.subscriptions[params.SubscriptionId]
+            result.RevisedPublishingInterval = sub.data.RevisedPublishingInterval
+            result.RevisedLifetimeCount = sub.data.RevisedLifetimeCount
+            result.RevisedMaxKeepAliveCount = sub.data.RevisedMaxKeepAliveCount
+
+            return result
+        except KeyError:
+            raise utils.ServiceError(ua.StatusCodes.BadSubscriptionIdInvalid)
+
     async def delete_subscriptions(self, ids):
         self.logger.info("delete subscriptions: %s", ids)
         res = []

asyncua/server/uaprocessor.py

@@ -328,6 +328,18 @@ async def _process_message(self, typeid, requesthdr, seqhdr, body):
             # _logger.info("sending create subscription response")
             self.send_response(requesthdr.RequestHandle, seqhdr, response)
 
+        elif typeid == ua.NodeId(ua.ObjectIds.ModifySubscriptionRequest_Encoding_DefaultBinary):
+            _logger.info("modify subscription request")
+            params = struct_from_binary(ua.ModifySubscriptionParameters, body)
+
+            result = self.session.modify_subscription(params, self.forward_publish_response)
+
+            response = ua.ModifySubscriptionResponse()
+            response.Parameters = result
+
+            #_logger.info("sending modify subscription response")
+            self.send_response(requesthdr.RequestHandle, seqhdr, response)
+
         elif typeid == ua.NodeId(ua.ObjectIds.DeleteSubscriptionsRequest_Encoding_DefaultBinary):
             _logger.info("delete subscriptions request (%s)", user)
             params = struct_from_binary(ua.DeleteSubscriptionsParameters, body)