n contains all information required to re-establish the connection without a full handshake for SSL versions up to and including TLSv1.2. In TLSv1.3 the same is true, but sessions are established after the main handshake has occurred. The server will send the session information to the client at a time of its choosing, which may be some while after the initial connection is established (or never). Calling these functions on the client side in TLSv1.3 before the session has been established will still return