FIN_WAIT_2

Many people are familiar with the 3-way handshake used to establish TCP, but may not be as familiar with the 4-way (occasionally 3-way) handshake used to close a TCP connection, ie. the bottom left section of this diagram: The happy case for shutting down a connection is that the client sends a FIN to the server and receives an ACK, then receives a FIN from the server and sends an ACK.