Data Transfer

To transfer data to or from HDLC, use read (2) and write (2). Each operation corresponds to an HDLC frame, which means that each read call will return only one packet, even if there is more data waiting and room in the buffer. If there is not enough room in the buffer for the current frame, read fails, and the frame is discarded. The buffer passed to a write call corresponds to a single HDLC frame. Calls to write with a length greater than the maximum frame size (hp_n1) fail.