TCP Flags
TCP flags are 9 control bits in the TCP header that manage connection state, flow control, and data transmission. Each flag has a specific purpose in the connection lifecycle, from establishment to termination.
Technical Details
Related Concepts
SYN (Synchronize)
Initiates a connection. Sent in the first step of the three-way handshake to synchronize sequence numbers between peers.
ACK (Acknowledgment)
Confirms receipt of data. Set in almost every packet after the initial SYN to acknowledge received bytes.
FIN (Finish)
Gracefully terminates a connection. Indicates the sender has no more data to send.
RST (Reset)
Abruptly terminates a connection. Sent when something goes wrong or a port is unreachable.
PSH (Push)
Requests immediate delivery of data to the application without waiting for the buffer to fill.
URG (Urgent)
Indicates urgent data that should be processed immediately. Rarely used in modern applications.