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.
