Figure shows the steps involved in the three-way handshake during a TCP connection establishment.  Step one shows the initiating client forming a SYN packet with a sequence number of 100 and sends the SYN request to client B.  Step two shows client B receiving the SYN and setting the sequence number to 300 and sending the SYN along with an ACK packet back to client A.  Step three shows client A receiving the SYN and ACK sent by client B, this establishes the connection.