• URG — Process the current TCP packet immediately. Directs the receiving system to examine the “urgent pointer” field.
• ACK — Acknowledgement. Directs the receiving system to examine the “acknowledgement number” field.
• PSH — Push. Elevate the priority of the packet’s data, but does not otherwise change rules around packet processing.
• RST — Reset. Terminates the connection forcefully.
• SYN — Synchronize. Used during the initial three-way handshake to set a shared (starting) sequence number.
• FIN — Finish. Indicates that the connection may be dropped gracefully.