if (session == null) {
// no session with endpoint available, create new empty session,
// start fresh handshake
session = new DTLSSession(peerAddress, true);
dtlsSessions.put(addressToKey(peerAddress), session);
handshaker = new ClientHandshaker(peerAddress, message, session);
} else {
if (session.isActive()) {
// session to peer is active, send encrypted message