 The advantage of software handshaking is that it can be done with absent or incompatible hardware handshaking circuits and cabling.The disadvantage, common to all in-band control signaling, is that it introduces complexities in ensuring that a) control messages get through even when data messages are blocked, and b) data can never be mistaken for control signals.The former is normally dealt with by the operating system or device driver; the latter normally by ensuring that control codes are "escaped" (such as in the Kermit protocol) or omitted by design (such as in ANSI terminal control).