we are using OPC UA stack 1.01.
A fact is that we did not register, i.e. we excluded the support of "transfer subscription" service. Now a OPC UA Client is trying to reconnect with our server, Client sent TransferSubscriptionRequest to our server and did not receive any repsonse. Is it a expected behavior of server?
That TransferSubscription service is not a required feature for UA Servers to implement, at least not for the Standard UA Server profile which is what I'm assumed you've built your product on. This profile is defined here although this is for UA version 1.03.
I would strongly encourage you to upgrade your UA stack to 1.03 so as to maintain interoperability with all the newer applications as they will not be interoperable with you in some situations, such as with insecure connections.
Karl is right. We even implemented a test in the CTT that invokes ALL of the UA Services sequentially to verify that a response is received that indicates either (a) success, e.g. read, (b) failure (not supported, not implemented, etc.)
Definitely upgrade to UA 1.03 stack version to increase your application's interoperability with other UA applications.