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The Free On-line Dictionary of Computing (foldoc)

1. Predetermined hardware or software activity designed to
establish or maintain two machines or programs in
synchronisation. Handshaking often concerns the exchange of
messages or {packets} of data between two systems with limited
{buffers}. A simple handshaking {protocol} might only involve
the receiver sending a message meaning "I received your last
message and I am ready for you to send me another one." A
more complex handshaking {protocol} might allow the sender to
ask the receiver if he is ready to receive or for the receiver
to reply with a negative acknowledgement meaning "I did not
receive your last message correctly, please resend it" (e.g. if
the data was corrupted en route).

{Hardware handshaking} uses voltage levels or pulses on wires
to carry the handshaking signals whereas {software
handshaking} uses data units (e.g. {ASCII} characters) carried
by some underlying communication medium.

{Flow control} in bit-serial data transmission such as
{EIA-232} may use either hardware or software handshaking.

2. The method used by two {modems} to establish contact with
each other and to agreee on {baud rate}, {error correction}
and {compression} {protocols}.

3. The exchange of predetermined signals between agents
connected by a communications channel to assure each that it
is connected to the other (and not to an imposter). This may
also include the use of passwords and codes by an operator.

[{Jargon File}]

(1995-01-13)