上一题的答案中SYN ACK seq FIN 是什么意思？

SYN, ACK, SEQ, and FIN are all flags used in the TCP (Transmission Control Protocol) protocol.

- SYN (Synchronize) is used to initiate a new connection between two devices.
- ACK (Acknowledgment) is sent in response to a received packet to confirm that it has been successfully received.
- SEQ (Sequence) is a value contained within each packet that helps in the reassembly of a received message.
- FIN (Finish) flags are used to signify the end of a connection.

In short, SYN and ACK are used in the three-way handshake process used to establish a connection, SEQ is used for packet ordering and to ensure packets are put back together correctly, and FIN is used to signify the end of a connection.