type Session interface {
	Close() error
	Write(msg [][]byte) error
	Read() (msg [][]byte, err error)
}

type SessionConfig struct {
	// The session (socket) type to use for negotiation. e.g. "REQ".
	SessionType string

	// The authentication mechanism to use for negotiation. e.g. "NULL".
	AuthMechanism string

	// Whether to take the server role for the purposes of the authentication
	// process.
	AuthIsServer bool

	// The identity string to report when negotiating the connection.
	Identity string

	// Parameters used by the PLAIN authentication protocol.
	AuthPlainUsername           string
	AuthPlainPassword           string
	AuthPlainServerValidateFunc func(username, password string) bool

	// Parameters used by the CURVE authentication protocol.
	AuthCurvek [32]byte
	AuthCurveS [32]byte

	// Dialer to use to make outgoing connections. If nil, net.Dial is used.
	Dialer net.Dialer

	// If set, this function will be called when the session receives a SUBSCRIBE
	// command from the remote side.
	SubscribeFunc func(name string) error

	// If set, this function will be called when the session receives a CANCEL
	// command from the remote side.
	CancelFunc func(name string) error
}