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TCP 스택을 포팅하거나 수정해야할 경우에는 중요하게 처리해야될  TCP State 값의 설명입니다.

 

TCP/IP State Transition Diagram (RFC793)

A connection progresses through a series of states during its lifetime. The states are: LISTEN, SYN-SENT, SYNRECEIVED, ESTABLISHED, FIN-WAIT-1, FIN-WAIT-2, CLOSE-WAIT, CLOSING, LAST-ACK, TIME-WAIT, and the fictional state CLOSED. CLOSED is fictional because it represents the state when there is no TCB, and therefore, no connection. Briefly the meanings of the states are:

 

LISTEN

represents waiting for a connection request from any remote TCP and port.

 

SYN-SENT

represents waiting for a matching connection request after having sent a connection request.

 

SYN-RECEIVED

represents waiting for a confirming connection request acknowledgment after having both received and sent a connection request.

 

ESTABLISHED

represents an open connection, data received can be delivered to the user. The normal state for the data transfer phase of the connection.

FIN-WAIT-1

represents waiting for a connection termination request from the remote TCP, or an acknowledgment of the connection termination request previously sent.

 

FIN-WAIT-2

represents waiting for a connection termination request from the remote TCP.

 

CLOSE-WAIT

represents waiting for a connection termination request from the local user.

 

CLOSING

represents waiting for a connection termination request acknowledgment from the remote TCP.

 

LAST-ACK

represents waiting for an acknowledgment of the connection termination request previously sent to the remote TCP (which includes an acknowledgment of its connection termination request).

TIME-WAIT

represents waiting for enough time to pass to be sure the remote TCP received the acknowledgment of its connection termination request.

CLOSED

represents no connection state at all.

 

 

A TCP connection progresses from one state to another in response to events. The events are the user calls, OPEN, SEND, RECEIVE, CLOSE, ABORT, and STATUS; the incoming segments, particularly those containing the SYN, ACK, RST and FIN flags; and timeouts.