BIO_free_all does just what it says: it frees the internal structure and releases all associated memory, including closing the associated socket.

A message sent on a datagram socket was larger than the internal message buffer or some other network limit, or the buffer used to receive a datagram into was smaller than the datagram itself.

CAUTION: all valves with fixed socket end connectors in the body must be installed in the open position to aid in evaporation of solvent vapors which can attack internal components.