What is the correct order of messages in the TCP three-way handshake?

The correct sequence of messages in the TCP three-way handshake is SYN -> SYN-ACK -> ACK. This process is fundamental in establishing a reliable connection between a client and a server.

The first step involves the client sending a SYN (synchronize) message to the server to initiate the connection. This message indicates that the client desires to establish a connection and includes an initial sequence number for synchronization purposes.

The server responds with a SYN-ACK (synchronize-acknowledge) message, which serves two purposes: it acknowledges the receipt of the client's SYN message and also sends its own SYN message back to the client, proposing a sequence number from the server's side.

Finally, the client sends an ACK (acknowledge) message back to the server, confirming that it has received the server's SYN-ACK. At this point, the connection is fully established, and data can be transmitted between the two parties.

This three-way handshake is essential for ensuring that both parties are ready for communication and have agreed upon the initial sequence numbers, which is crucial for maintaining the integrity and order of data transmission in TCP.