TCP 천이도

TCP 천이도.pptx

1) socket 이란?

A socket is one endpoint of a two-way communication link between two programs running on the network. A socket is bound to a port number so that the TCP layer can identify the application that data is destined to be sent to.

2) socket 상태 

상태	설명
ESTABLISHED	The socket has an established connection
SYN_SENT	The socket is actively attempting to establish a connection
SYN_RECV	A connection request has been received from the network
FIN_WAIT1	The socket is closed, and the connection is shutting down
FIN_WAIT2	Connection is closed, and the socket is waiting for a shutdown from the remote end
TIME_WAIT	The socket is waiting after close to handle packets still in the network 자신이 전송한 ACK 패킷이 상대방에 도달하기를 기다린다.
CLOSED	The socket is not being used
CLOSE_WAIT	The remote end has shut down, waiting for the socket to close
LAST_ACK	The remote end has shut down, and the socket is closed, waiting for acknowledgement
LISTEN	The socket is listening for incoming connections
CLOSING	Both sockets are shut down but we still don't have all our data sent
UNKNOWN	The state of the socket is unknown

출처 : linux 의 netstat 메뉴얼