3 way hand shake

The TCP three-way handshake in Transmission Control Protocol is the method used by TCP to set up a TCP/IP connection over an Internet Protocol based network. 

It is also called the TCP-handshake; three message handshake and/or SYN-SYN-ACK.

This 3-way handshake process is also designed so that both ends can initiate and negotiate separate TCP socket connections at the same time.

• SYNchronize and ACKnowledge messages are indicated by a either the SYN bit, or the ACK bit inside the TCP header.

• SYN-ACK message has both the SYN and the ACK bits turned on (set to 1) in the TCP header.

• UDP does not perform this 3-way handshake and for this reason, it is referred to as an unreliable protocol.