fixed FromDeviceRPCResponseProto.response handling in case of null

application/src/main/java/org/thingsboard/server/service/queue/DefaultTbCoreConsumerService.java

@@ -466,9 +466,9 @@ public class DefaultTbCoreConsumerService extends AbstractConsumerService<ToCore
     }
 
     private void forwardToCoreRpcService(FromDeviceRPCResponseProto proto, TbCallback callback) {
-        RpcError error = proto.getError() > 0 ? RpcError.values()[proto.getError()] : null;
+        RpcError error = proto.getError() >= 0 ? RpcError.values()[proto.getError()] : null;
         FromDeviceRpcResponse response = new FromDeviceRpcResponse(new UUID(proto.getRequestIdMSB(), proto.getRequestIdLSB())
-                , proto.getResponse(), error);
+                , proto.hasResponse() ? proto.getResponse() : null, error);
         tbCoreDeviceRpcService.processRpcResponseFromRuleEngine(response);
         callback.onSuccess();
     }

application/src/main/java/org/thingsboard/server/service/queue/DefaultTbRuleEngineConsumerService.java

@@ -180,9 +180,9 @@ public class DefaultTbRuleEngineConsumerService extends AbstractPartitionBasedCo
             callback.onSuccess();
         } else if (nfMsg.hasFromDeviceRpcResponse()) {
             TransportProtos.FromDeviceRPCResponseProto proto = nfMsg.getFromDeviceRpcResponse();
-            RpcError error = proto.getError() > 0 ? RpcError.values()[proto.getError()] : null;
+            RpcError error = proto.getError() >= 0 ? RpcError.values()[proto.getError()] : null;
             FromDeviceRpcResponse response = new FromDeviceRpcResponse(new UUID(proto.getRequestIdMSB(), proto.getRequestIdLSB())
-                    , proto.getResponse(), error);
+                    , proto.hasResponse() ? proto.getResponse() : null, error);
             tbDeviceRpcService.processRpcResponseFromDevice(response);
             callback.onSuccess();
         } else if (nfMsg.getQueueUpdateMsgsCount() > 0) {

common/proto/src/main/java/org/thingsboard/server/common/util/ProtoUtils.java

@@ -583,10 +583,11 @@ public class ProtoUtils {
     }
 
     private static ToDeviceActorNotificationMsg fromProto(TransportProtos.FromDeviceRpcResponseActorMsgProto proto) {
+        TransportProtos.FromDeviceRPCResponseProto rpcResponse = proto.getRpcResponse();
         FromDeviceRpcResponse fromDeviceRpcResponse = new FromDeviceRpcResponse(
-                new UUID(proto.getRpcResponse().getRequestIdMSB(), proto.getRpcResponse().getRequestIdLSB()),
-                proto.getRpcResponse().getResponse(),
-                proto.getRpcResponse().getError() >= 0 ? RpcError.values()[proto.getRpcResponse().getError()] : null);
+                new UUID(rpcResponse.getRequestIdMSB(), rpcResponse.getRequestIdLSB()),
+                rpcResponse.hasResponse() ? rpcResponse.getResponse() : null,
+                rpcResponse.getError() >= 0 ? RpcError.values()[rpcResponse.getError()] : null);
         return new FromDeviceRpcResponseActorMsg(
                 proto.getRequestId(),
                 TenantId.fromUUID(new UUID(proto.getTenantIdMSB(), proto.getTenantIdLSB())),

common/proto/src/main/proto/queue.proto

@@ -1238,7 +1238,7 @@ message LocalSubscriptionServiceMsgProto {
 message FromDeviceRPCResponseProto {
   int64 requestIdMSB = 1;
   int64 requestIdLSB = 2;
-  string response = 3;
+  optional string response = 3;
   int32 error = 4;
 }
 

common/proto/src/test/java/org/thingsboard/server/common/util/ProtoUtilsTest.java

@@ -226,6 +226,17 @@ class ProtoUtilsTest {
         assertThat(ProtoUtils.fromProto(serializedMsg)).as("deserialized").isEqualTo(msg);
     }
 
+    @Test
+    void protoFromDeviceRpcResponseOnewaySerialization() {
+        // Oneway RPC success: response and error are both null. Relies on the proto
+        // 'optional string response' presence bit so the receiver round-trips null
+        // rather than seeing the proto3 default "".
+        FromDeviceRpcResponseActorMsg msg = new FromDeviceRpcResponseActorMsg(23, tenantId, deviceId, new FromDeviceRpcResponse(id, null, null));
+        TransportProtos.ToDeviceActorNotificationMsgProto serializedMsg = ProtoUtils.toProto(msg);
+        Assertions.assertNotNull(serializedMsg);
+        assertThat(ProtoUtils.fromProto(serializedMsg)).as("deserialized").isEqualTo(msg);
+    }
+
     @Test
     void protoRemoveRpcActorSerialization() {
         RemoveRpcActorMsg msg = new RemoveRpcActorMsg(tenantId, deviceId, id);