To establish a connection, TCP uses a 3-way handshake. Before a client attempts to connect with a server, the server must first bind to a port to open it up for connections: this is called a passive open. Once the passive open is established then a client may initiate an active open. To establish a connection, the 3-way (or 3-step) handshake occurs:The active open is performed by sending a SYN to the server. In response, the server replies with a SYN-ACK. Finally the client sends an ACK back to the server. At this point, both the client and server have received an acknowledgement of the connection.