In information technology, telecommunications, and related fields, handshaking is an automated process of negotiation that dynamically sets parameters of a communications channel established between two entities before normal communication over the channel begins. It follows the physical establishment of the channel and precedes normal information transfer.
The handshaking process usually takes place in order to establish rules for communication when a computer sets about communicating with a foreign device . When a computer communicates with another device like a modem, printer, or network server, it needs to handshake with it to establish a connection.
Handshaking can negotiate parameters that are acceptable to equipment and systems at both ends of the communication channel, including, but not limited to, information transfer rate, coding alphabet, parity, interrupt procedure, and other protocol or hardware features. Handshaking is a technique of communication between two entities. However, within TCP/IP RFCs, the term "handshake" is most commonly used to reference the TCP three-way handshake. For example, the term "handshake" is not present in RFCs covering FTP or SMTP. One exception is Transport Layer Security, TLS, setup, FTP RFC 4217. In place of the term "handshake", FTP RFC 3659 substitutes the term "conversation" for the passing of commands.