As its name suggests, TCP has its greatest impact at the transport layer. Before sending any data, TCP establishes a short connection between two network endpoints via a three-way handshake.
First, the client initiates a connection by sending a SYN (synchronization) message (in the form of a random number) - when received, the server acknowledges it with a SYN-ACK (which simply adds 1 to the end of the client number). Finally, this SYN-ACK is acknowledged by the client with an ACK message. This virtual handshake ensures that both the sender and receiver are ready to communicate and know that the channel is established. If the receiving port is disconnected or unreachable, the ACK message is replaced by a TCP RST (reset) packet.
Not only is the initial process based on a two-way acknowledgement: a two-way greece telegram data termination also acknowledges that the client or server has also finished sending data. In a similar pattern, after all relevant pieces of data have been sent, the client sends them via a FIN segment in the form of its own sequence number. Again, the server acknowledges this. When all the data has been received by the server, it is the server's turn to send a FIN packet, which is acknowledged and the connection is terminated.