+---------+ ---------\ active OPEN | CLOSED | \ ----------- +---------+<---------\ \ create TCB | ^ \ \ snd SYN passive OPEN | | CLOSE \ \ ------------ | | ---------- \ \ create TCB | | delete TCB \ \ V | \ \ +---------+ CLOSE | \ | LISTEN | ---------- | | +---------+ delete TCB | | rcv SYN | | SEND | | ----------- | | ------- | V +---------+ snd SYN,ACK / \ snd SYN +---------+ | |<----------------- ------------------>| | | SYN | rcv SYN | SYN | | RCVD |<-----------------------------------------------| SENT | | | snd ACK | | | |------------------ -------------------| | +---------+ rcv ACK of SYN \ / rcv SYN,ACK +---------+ RFC793 | -------------- | | ----------- TCP Connection State Diagram | x | | snd ACK | V V | CLOSE +---------+ | ------- | ESTAB | | snd FIN +---------+ | CLOSE | | rcv FIN V ------- | | ------- +---------+ snd FIN / \ snd ACK +---------+ | FIN |<----------------- ------------------>| CLOSE | | WAIT-1 |------------------ | WAIT | +---------+ rcv FIN \ +---------+ | rcv ACK of FIN ------- | CLOSE | | -------------- snd ACK | ------- | V x V snd FIN V +---------+ +---------+ +---------+ |FINWAIT-2| | CLOSING | | LAST-ACK| +---------+ +---------+ +---------+ | rcv ACK of FIN | rcv ACK of FIN | | rcv FIN -------------- | Timeout=2MSL -------------- | | ------- x V ------------ x V \ snd ACK +---------+delete TCB +---------+ ------------------------>|TIME WAIT|------------------>| CLOSED | +---------+ +---------+