handshaking n.

[very common] Hardware or software activity designed to start or keep two machines or programs in synchronization as they do protocol. Often applied to human activity; thus, a hacker might watch two people in conversation nodding their heads to indicate that they have heard each others' points and say "Oh, they're handshaking!". See also protocol.

--The Jargon File version 4.3.1, ed. ESR, autonoded by rescdsk.