message

const (
	// KindGet is a message from the client to the server, stating the client wants
	// to know the latest version of the value for a given key. It is never sent
	// from the server to the client. This kind of message should only be issued
	// when the client does not have a version of the value for the given key, or
	// the client knows the version is stale, e.g., because of a put error.
	KindGet Kind = iota

	// KindPut is a message that can be sent both by the client and the server. It
	// is used by clients to update a key's corresponding value with a new version.
	// The server responds with the exact same put message if the put is accepted,
	// or with and error message. The server also fans out accepted put messages to
	// all clients that are connected, so they can keep up to date. This way,
	// clients should not need to issue get messages often.
	KindPut

	// KindError is a message that is only sent from the server to the client. That
	// can be in response to a get message (in case the requested key is not known)
	// or in response to a put message (in case the put version number is wrong).
	// The version number in a put message should match the one in the server,
	// proving that the client is up to date. If the put is stale, the client may
	// be overwriting some value, so the client should get the latest version and
	// possibly redo the put with the correct version, or give up the put). Other
	// error conditions might arise.
	KindError

	// KindAuth is sent with a password value from client to server (only over a
	// TLS connection) to authorize the client. It is sent with an empty value
	// from server to client upon successful authorization. If the password does
	// not match, the server response will be of KindError.
	KindAuth
)