fix: invalid assignment of client_id

[jaeheonji]

This PR is related the invalid assignment of client_id.
As the above log, the problem occurs when attaching to a session.

The cause of the problem is the assert_socket function, which checks whether the socket is connected before attaching.
Ideally, this should work like this:

But, currently like this:

To solve this problem, assert_socket has to wait for a message from the server.