Tcp flags in networking

1. Synchronize or “SYN”:
It notifies the transmission of a new sequence number. This flag generally
represents the establishment of a connection (three-way handshake) between
Acknowledgement or “ACK”:
It confirms the receipt of the transmission and identifies the next expected
sequence number. When the system successfully receives a packet, it sets the
value of its flag to “1,” thus implying that the receiver should pay attention to it.
Push or “PSH”:
When it is set to “1,” it indicates that the sender has raised the push operation
to the receiver; this implies that the remote system should inform the receiving
application about the buffered data coming from the sender. The system raises
the PSH flag at the start and end of data transfer and sets it on the last
Urgent or “URG”:
It instructs the system to process the data contained in packets as soon as
possible. When the system sets the flag to “1,” priority is given to processing
Finish or “FIN”:
It is set to “1” to announce that no more transmissions will be sent to the
remote system and the connection established by the SYN flag is terminated.
Reset or “RST”:
When there is an error in the current connection, this flag is set to “1” and the
connection is aborted in response to the error. Attackers use this flag to scan
hosts and identify open ports. SYN scanning mainly deals with three flags:
SYN, ACK, and RST.
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