Operational data subscription issue

[cohult]

A good rule to follow is using “one thread per socket”. No sharing of sockets between threads.

From ConfD UG chapter The Protocol and a Library Threads Discussion:

ConfD API functions are thread-safe as such, but multiple threads using them with the same socket will have unpredictable results, just as multiple threads using the read() and write() system calls on the same file descriptor in general will. In the ConfD case, one thread may end up getting the response to a request from another, or even a part of that response, which will result in errors that can be very difficult to debug.

If you had searched the forum for your error message, you would have found out what your issue is. (besides using an old End-of-Support, End-of-Maintenance version of ConfD)
See for example here:

Cdb_sync_subscription_socket return Unexpected data on socket

The reason is likely that the application is mixing up its CDB and/or MAAPI sockets - e.g. two threads trying to use the same socket at the same time. What it means is that a CDB or MAAPI API function makes a request to ConfD, and gets a response back from ConfD that doesn’t match the request. The examples.confd/intro/9-c_threads/ example shows how one should handle these sockets when using multiple threads.