Reset segment:
Some special cases, TCP reset packets to send one end to the other end, close link to notify the other party or to re-establish the link.
Produced three cases the reset message:
1. When a client access port that does not exist, the target host will give the client sends a reset packet segment.
And the reset packet is irreversible, because he tells the client the head, the server side of the receive window is zero.
// connectio refuse port does not exist disavow
So the party received a reset segment should be shut down links or re-establish the link.
In fact, the client initiates a connection to the server is in the TIME_WAIT state, will receive a reset message
After both sides completed exchange data under 2. Normally, the client sends a FIN to end link
TCP provides a way to terminate the connection anomaly, the other is to send a reset segment, and the like all queued data to be transmitted the transmitting side discards all
3. The server due to a network failure or other abnormal power off, and client abort the link, but the client still maintains the original link, even if the server is restarted, information about the link has long been forgotten server. (Half-open state)
If at this time the client sends the data link semi-open state, you will receive a reset message the other party to respond.