Can you list the main TCP protocol flags and explain their purposes?

The main setup flags (control flags) in the TCP header and their purposes:

• SYN (Synchronize) — used to establish a connection. Marks the beginning of the three-way handshake.
• ACK (Acknowledgment) — confirms receipt of data. Indicates that the acknowledgment field is valid.
• FIN (Finish) — signals the end of data transmission and connection closure.
• RST (Reset) — resets the connection, used in case of errors or inability to establish a connection.
• PSH (Push) — requests immediate data transfer to the recipient application without buffering.
• URG (Urgent) — indicates that the data has high priority and should be processed first.

Example: when establishing a connection, the client sends a packet with the SYN flag, the server responds with SYN+ACK, and the client confirms with ACK — this is the TCP three-way handshake.