A computer handshake refers to the process of one computer attempting to establish a connection with another computer or device. During the "handshake" process, the computers and devices involved synchronize with one another and establish the protocols of the communication. These protocols may include speed of data transfer, the coding alphabet to be used and parity.
A computer handshake is also called the "SYN, SYN, ACK, ACK" handshake. The "SYN, SYN, ACK, ACK" term stands for one computer sending a SYNchronize packet to a second computer, wherein the computer receiving the packet sends a SYNchronize ACKnowledge packet back to the first computer, which again sends an ACKnowledge packet back to the second computer.
The communication protocols established with the handshake between two computer or devices may be simple or complex. For instance, the communication protocol establishes that only one computer can send data continuously to the other computer. A more complex handshake may involve either computers or devices communicating back and forth continuously.
Computer handshakes can be best described and observed during the era of dial-up modem Internet whenever a computer modem tried to establish a connection to the Internet. After the modem dialed the designated Internet access number, it emitted a high-pitched sound as it tried to establish a connection. The modem would then fall silent after making a couple of clicking sounds, which meant that the handshake was successful and that the connection was established.