+ virtual int write (const byte *msg, size_t msglen, timestamp_t timestamp) = 0;
+
+ /** Read raw bytes from a port.
+ * @param buf memory to store read data in
+ * @param bufsize size of @a buf
+ * @return number of bytes successfully read, negative if error
+ */
+ virtual int read (byte *buf, size_t bufsize) = 0;
+
+ /** block until the output FIFO used by non-process threads
+ * is empty, checking every @a check_interval_usecs usecs
+ * for current status. Not to be called by a thread that
+ * executes any part of a JACK process callback (will
+ * simply return immediately in that situation).
+ */
+ virtual void drain (int /* check_interval_usecs */) {}