Can TLS session resumption work after client dropped connection & reconnected to server? I'm developing a sensor node and investigating TLS/OpenSSL. The network the node runs behind could drop and reconnect a lot. The node has limited data plan so data overhead is the key where TLS handshake is a big contributor as I understand.  

Can session resumption be used after each network drop &amp; reconnection? Or full handshake is needed in this case?
A TLS session can be resumed once both sides know of the session. The exchange of the necessary information (i.e. session identifier or session ticket) is done within the initial handshake. This means a session can already be re-used within other connections once this initial handshake is done.

How long the session information are kept and if they are discarded if a connection is closed uncleanly depends on the specific implementation and is unrelated to the cryptography itself.