Connection Termination


Half Close
TCP terminates data flow in one direction one by one
A Connection is terminated by exchanging 4 packets
2 communication nodes play a different role
active close side 
Send first FIN(indicate finish of the connection)
Active close side wait for a while (2MSL time) after it sends last ACK
passive close side 
Send ACK for FIN and then send second FIN
Passive close side wait for last ACK
Normally client side should do "active close"
lighten the burden on server side