The TCP three way handshake is the process for establishing a TCP connection. A TCP connection is established as shown in the below example. In this example, we assume a client computer is contacting a server to send it some information. The client sends a packet with the SYN bit set and a sequence number of N. The server sends a packet with an ACK number of N+1, the SYN bit set and a sequence number of X. The client sends a packet with an ACK number of X+1 and the connection is established. The client sends the data. The first three steps in the above process is called the three way handshake which is used to establish a TCP connection.